Illustration by Paul Kisselev.

Charlie O’Donnell has long eyelashes, an athletic build and a shiny shaved head: a 32-year-old in his prime working at one of the most highly-respected startup investment firms in New York, First Round Capital. The kayaking enthusiast and devotee of the fitness Bible The 4-Hour Body is known to broadcast his nine-mile cycling commute on Twitter, where he goes by @ceonyc, a reference to his initials.

A power networker, Mr. O'Donnell has made himself a fixture at tech parties in search of the next Mark Zuckerberg, or as it were, the next Margaret. Trouble is, he's also looking for the next Mrs. O'Donnell.

“For men, if we are single, any single female that we are hanging out with has the potential, at least at first, to be a potential date,” Mr. O'Donnell wrote in 2004 on his popular blog, This Is Going To Be Big. “But for girls, you never really know. You can be doing all of the dating type stuff... showing interest, asking them out, etc... and they'll seemingly go along with the whole thing, until the point that you're sitting across from them and you realize, ‘Hey... wait a second... this isn't a date at all!’”

Business and pleasure often mix in the Silicon Alley startup scene, where investors are known to karaoke with their portfolio companies. By now, everyone knows a pitch and a drink can be one and the same—but what about a pitch and a date? With more women on the tech scene, uncertainty is increasingly common.

“I once scheduled a meeting with someone and it turned out to be a date,” one well-connected female techie told Betabeat. That someone was Mr. O’Donnell. One female founder was “asked out to dinner on the pretense of it being a meeting, but it turned out to be a date” with a local venture capitalist, who followed up with an extended series of flirtatious text messages. That man also turned out to be Mr. O’Donnell. In fact, Mr. O'Donnell's name came up repeatedly in the course of reporting a more general story about women in tech.

Even so, there are far more nefarious scoundrels on the scene. Betabeat heard some stories of other investors that sounded like fodder for Mad Men. “I've even heard of VCs trying to sleep with their potential female investees,” said one female founder who used to live in New York and now lives in the Bay Area. “Pretty sketchy stuff.” One woman who organizes tech events said she was stalked for years by a consultant who stopped only after her brother intervened; one female founder met with a Silicon Valley investor who followed up with an invitation to his hotel room via a midnight text message—“and he was married!”

By contrast, Mr. O'Donnell's dalliances aren't perverse—just pervasive. And by most any standard, the energetic VC would seem to be a catch. A Brooklyn boy at heart, he still lives in Bay Ridge near his family. “To my mother’s chagrin, I’m her last hope for local grandchildren,” he told Betabeat in an interview. A product of the Jesuit-run Regis High School on the Upper East Side, he started at the General Motors Pension Fund as an intern in high school and eventually landed a job there. He works hard, plays hard (in addition to kayaking, he runs a pick-up softball game and a dodgeball team), has good taste in restaurants and seems earnest about matters of the heart. “I want to find someone who not only loves me, but lets themselves experience love and doesn't worry about the chances of things actually working out,” he blogged in 2008.

[Disclosure: While Betabeat was reporting this story, we discovered that an Observer Media employee had briefly dated Mr. O’Donnell. She had no involvement in this article.]

Mr. O’Donnell is exceptionally well-connected in the scene and yet still puts his calendar online so anyone can request some face time. He's something of an industry gatekeeper—or as he puts it, “more like a concierge.” Mr. O’Donnell, though he says he doesn’t drink, attends a vast number of events; socializing is practically a job requirement. “The reason I get the results that I do is because I’m a part of the scene,” he told Betabeat. “I have a big social network, and that leads to a lot of inbound. I get an early look at a lot of good deals because I am out at the parties.”

To hear the city’s female entrepreneurs tell it, an ambiguous date-meeting with Mr. O’Donnell is almost a rite of passage—like living on ramen while you launch your first app. One female founder recalled a recent girls’ night out with a mix of tech and non-tech friends, during which Mr. O’Donnell came up in conversation. “We were talking about how he was trying to hit on [one female entrepreneur who was present],” she said, when one of the women who did not work in the tech scene recalled a similar situation she’d encountered in college years ago. “She said, ‘I was the president of my investment club and this guy came to speak. He was bald and he worked at GM and he came up to me afterward and asked me out to dinner, and made it seem like it kind of was a mentoring thing, but it was a date, and it was really weird and really uncomfortable.’” The guy turned out to be Mr. O’Donnell, too. Of the seven women at dinner, the source said, five had stories about fielding Mr. O’Donnell’s attentions.

Not that attention from a young, long-lashed VC is always a bad thing. “My friends and I sometimes joke, we don’t always mind the ratio,” admitted Sarah Wulfeck, a director from a digital agency, referring to the gender disparity. “I think lots of women in tech feel that way sometimes, too, if they're honest. What do you do at an event with a lot of smart young professionals who are drinking and schmoozing and talking about money and dreams? Human social behavior is what it is.”

We turned to Nancy Slotnick, who works as a dating coach and is the founder of Facebook application MatchMaker Cafe, for perspective on how personal the professional should get. “I'm kind of all for flirting,” she said. “I think women don’t do it enough!”

If you’re not sure whether you’re on a date, just ask, she said. “There's so many situations where you could be trying to figure out, is this a date or not a date,” she said. “These days, people work so much, especially entrepreneurs, and if you’re trying to meet someone for dating, you have to do a fair amount of switch-hitting.”

Many New Yorkers complain about the murkiness of modern dating rules, but the issue is particularly dicey in the tech scene, which feels morally tormented by its gender imbalance. Between panels everywhere from South By Southwest (“Has The Glass Ceiling Ever Smacked You In The Butt?”) to the White House (with Valerie Jarrett), countless stories in the tech press (“Not Enough Women In Tech? Stop Blaming the Men,” “Tech Really Is A Man's Man's Man's World”), and awareness campaigns like Change the Ratio, handwringing is endemic. “Nothing seems to irritate nerds more than the idea that they're oppressing people,” one techie mused recently on a forum discussion about women in tech. “It probably has something to do with the fact that so many of them were picked on growing up.”

Most women in tech try too hard to separate work and romance, in Ms. Slotnick’s opinion. But she acknowledged that things can get complicated when the players are a founder and a VC.

“That’s not a switch-hitter situation,” she said firmly. “That’s a situation where you have to choose: date the guy and put the situation on hold, or if you want to get his money, focus on that and put the dating stuff on hold.

“But that doesn't mean you can’t flirt,” she added.

But in light of his influential position, Mr. O’Donnell’s flirtatiousness has come close to getting him in trouble. One woman complained to Josh Kopelman, the managing director at First Round. When Mr. O’Donnell was confronted, he tried to guess who had complained—and guessed wrong. Another well-connected woman in the New York tech scene said she has spoken to Mr. O’Donnell about toning it down. “A few women who have offered their guidance and feedback to him only to be met with defensiveness and a refusal to hear it," she said.

What seemed to grate on many of Mr. O’Donnell’s targets was the sense that they’d been subjected to a romantic version of the bait-and-switch: expecting a meeting, they’d found themselves on a date. We heard other complaints, similarly mild—flirting over Facebook, flirting over latenight Gchat, flirting over email. A male founder-turned-VC was particularly irked because Mr. O’Donnell had hit on his wife. One female founder told Betabeat she had never had a bad experience with Mr. O’Donnell, because she had studiously avoided him. “I heard that there were stories,” she said. “Which is why I never took a meeting with him. But I don't know what the stories actually were. Just heard about heebie jeebies. Ughhh. I like, won't walk near him.”

The vagueness of the accusations is perhaps why Mr. O’Donnell, having established his reputation as a notorious asker-outer, has been unable to detect what’s rubbing some female founders the wrong way. No one accused him of molestation, or harassment, or even talking dirty (with one very nerdy exception).

The greatest offense Mr. O’Donnell actually stands accused of seems to be that of casting a very wide net—which raises the question of whether his detractors aren’t perhaps overreacting. "It's a joke. No one takes it seriously,” one female founder said, of Mr. O’Donnell.

Navigating such relationships is simply part of the territory, she said. “Initially, I remember it being a barrier for me. But I also found that once you prove yourself and you prove that you know what you're talking about, it works to your advantage, because the industry is so male-dominated that when a woman comes into the room, everyone pays attention.”

On a recent Friday, Mr. O’Donnell hosted a luncheon at Vapiano’s, the chic Italian eatery near Union Square where he frequently holds court. The lunch had a special purpose: Mr. O'Donnell wanted to meet more women founders as well as introduce them to other women. “I'm interested in creating more opportunities for entrepreneurs, especially women, to connect to investors early to build relationships—less name-dropping pitches, more casual lunches,” he wrote in an email invitation.

Seated against the window in the middle of the gaggle, Mr. O’Donnell thanked everyone for coming and gave a brief speech about how First Round had just invested in two female-led companies, neither of which had been referred by other women. “Stop being competitive!” he said, and asked the attendees to introduce themselves one-by-one. The group ate, drank and chatted for about an hour and a half. One attendee praised First Round Capital to Betabeat for its hospitality toward women, unlike Spark Capital and IA Ventures, which she referred to as “frat houses.”

After lunch, Betabeat asked Mr. O’Donnell privately about the stories we'd been hearing. He vehemently denied he’d ever blurred the lines. (“I take meetings in my office!” he cried immediately, his voice cracking, when we broached the subject of date-meetings.) Over the weekend, he sent out a mass email claiming a spiteful adversary was slandering him to tech journalists—to our knowledge, this individual is his invention—and asking women to speak on his behalf.

Over the next three days, Betabeat received about 30 emails from women (including Ms. Slotnick and Ms. Wulfeck) defending Mr. O’Donnell as a great supporter of women.

“If you're planning on writing a story about someone in the venture community who has been unresponsive to women, you're honestly looking at the wrong guy,” wrote Jen McFadden, VP of strategic initiatives at Xconomy. “When I first moved to New York as an entrepreneur, looking to build a network, Charlie was the first one to reach out,” wrote Carmen Magar, a consultant for McKinsey's Business Technology Office.

Other women shared stories of how Mr. O’Donnell gotten them jobs, encouraged them to start a company or made a crucial introduction. Betabeat reached out to as many of the emailers as we could, although Mr. O’Donnell had instructed them to “ignore any follow up.”

Some told us flatly that Mr. O’Donnell had never made an advance. But upon clarification that the story was not planted by a vengeful enemy of Mr. O’Donnell’s, and that the scuttlebutt wasn’t about his unresponsiveness to women, but rather his overresponsiveness, two of the emailers acknowledged that Mr. O’Donnell “has a problem,” as one put it.

One well-regarded female member of the New York tech scene rushed to defend Mr. O’Donnell, who she considers a friend. “Charlie does have a reputation for asking a lot of women in tech out,” she said in an email. “But he also has a reputation of supporting a lot of women in tech. It's really important you highlight this. He's helped me and my female tech friends in a number of ways that have had a profound impact.” Mr. O’Donnell recommended her to an employer a few years ago, introduced her to a crucial female friend and mentor, and advised a friend of hers to fight for a better title.

“And back to him and dates,” she said. “He's not sleazy about it. If anything, it's a bit comical because that's what Charlie does. And that's important. I've known Charlie for years and he's a good guy who means well.”

It’s increasingly difficult for a single VC to keep dating and dealflow separate, as tech bleeds into every industry and more and more enterprising New Yorkers are seduced by the startup siren song.

“I met someone who was working outside tech, we started dating, and three or four weeks into it she mentions she has a startup on the side,” Mr. O’Donnell told Betabeat. “To be honest, I was hurt, like, ‘I could help you, you know, this is what I do for a living.’ She didn’t want me to think the reason she was interested in me was because of her startup.

“My thing has always been, I’m a person first and a professional second,” Mr. O’Donnell explained. “And these days, tech is so pervasive. I mean, where do you draw the line? Someone with a startup from Conde Nast? People coming from PR and marketing? A company with a website? If you kept your dating life relegated to Luddites, you would get pretty lonely.”