The gang as it once was (via Technology Review)

Venture capitalists have come down with a bout of  seriously itchy feet. Just this week, we heard Union Square Ventures was raising a new fund, we broke the news that Andy Weissman was leaving betaworks for UVS,  Polaris Venture Partners' Mike Hirshland announced he was leaving the Boston fund to launch a new seed firm, and today AllThingsD's Peter Kafka reports that Twitter will lose Fred Wilson (one of its earliest backers) and Bijan Sabet from its board by the end of the month.

According to Mr. Kafka's sources, "there's no bad blood behind the move." Over time, the board had swelled to include Flipboard’s Mike McCue, former DoubleClick CEO David Rosenblatt and ubiquitous Valley Peter Currie along with Benchmark’s Peter Fenton and CEO Dick Costolo. In fact, the company will not be filling Mr. Wilson's and Mr. Sabet's soon-to-be empty seats. That leaves Twitter, which has seen a number of executive unrest over the years, a "little less unwieldy."

Both Mr. Wilson's fund, Union Square Ventures, and Mr. Sabet's fund, Spark Capital, have sold some of their holdings in Twitter, which is now valued at $8.4 billion, via the secondary market, but "continue to hold a majority of their stakes," reports Mr. Kafka.

Via Twitter, Fortune's Dan Primack proffered an explanation for their departure, tweeting, "twitter board shakeup reflected in who was offered cash-out on last VC round." According to Mr. Primack, while "no one cashed out entirely," only some investors, including USV and Spark were given the "option of cashing out," while others like Benchmark and Insight weren't. He says "the option was just to sell up to (approx.) 20% of stakes," although what percentage they exercised is still unknown.