image via Bijan Sabet's Tumblr

Along with their announcement of a $85 million series E funding round earlier this week, Tumblr offered some statistics on their explosive growth. Most impressively, perhaps, was the fact that the site now does 12-13 BILLION page views per month, an astronomical increase over this time last year.

But these numbers are perhaps even more staggering: Tumblr has only around 13 million users and 30 million monthly unique visitors producing this massive pageview count. The people who spend time on Tumblr, it seems, are highly-engaged, and that's what convinced the venture capitalists from Greylock Partners, who led this round,  that real revenue and even profitability, is just around the corner. "They will succeed in working through that over the next months and years,” John Lilly, a partner at Greylock, told Reuters.

Bijan Sabet, of Spark Capital, one of the company's original investors who sits on Tumblr's board, said the rapid growth over the last year has given Tumblr the scale they need to monetize. "I think now the important role models are companies like Google and Facebook. Once you have a network at scale, you can begin to advertise in a way that doesn't feel invasive, that adds value instead."

Although Tumblr founder David Karp has said on several occasions that he doesn't want advertising thrown up on people's blogs, Mr. Sabet says that was natural at the time. "People need to remember that a year ago this company was tiny, around ten people who had raised ten million dollars. I don't think there is any shame in the fact that they choose to focus on users and product as opposed to generating revenue."

The critical question now is how to monetize a Tumblr pageview. As Mr. Sabet pointed out, the majority of these pageviews happen inside the Tumblr dashboard. So in many ways, users consume content here more like a stream of messages on Twitter than a traditional media property, where one page links to the next and users are driven from article to article.

Another issue with the dashboard is context. Google search is a powerful mechanism to pair against advertising because a search query offers a very specific context about what users are interested in. A typical Tumblr dashboard, by comparison, might have feeds from blogs about design, travel, sex and food all sandwiched together.

Tumblr could play with the idea of promoted posts or tags, much as Twitter has done. But Mr. Sabet believes it will pursue its own path. "At a certain base level, what you're selling to advertisers is engagement, and Tumblr has that in spades. I think as Tumblr matures you'll see them follow these other large networks and create their own kind of data center, their own breed of ad products."

The growth is paired with a push by Arianna Huffington to craft verticals around every type of audience. The site has recently launched HuffPost Gay Voices, HuffPost Weddings and HuffPost High School, among the more than twenty new categories it has brought online since being purchased by AOL.

International expansion is also ramping up. Ms. Huffington was in Brazil when the whole Crunchfund drama erupted and is planning more trips abroad in the coming weeks.

There was no indication in the press release of how much of this new traffic comes from AOL's considerable network. If the growth is simply the result of the new partnership, then  it's less interesting than new organic highs.

As Kara Swisher points out, HuffPo is also acquiring companies and continuing its hiring binge, taking full advantage of its big new bottom line.