(Corrects number of Quora co-founders from four to two)

SAN FRANCISCO - As Wall Street eagerly awaits signs that Internet sensation Facebook will offer shares to the public, the venture capitalists that prowl California's Silicon Valley are keeping close tabs on another hot commodity: the employees leaving Facebook.

A handful of start-up companies founded by Facebook alumni are attracting attention and generating a good amount of buzz within venture circles, where competition is fierce to get a stake in the web's next hit product.

On Monday, Quora, a start-up founded by two ex-Facebook employees, including former Chief Technology Officer Adam D'Angelo, raised a Series A round of funding from Benchmark Capital that the technology blog TechCrunch said valued the company at $86 million, citing an unnamed source.

Benchmark partner and former Facebook product management vice president Matt Cohler will sit on Quora's board.

Quora, which operates out of a small, college-dorm-like suite in downtown Palo Alto, California, with cardboard crates of water-bottles stacked waist-high against the walls, had not planned to raise money so early, said D'Angelo, who is the CEO of Quora.

We weren't really shopping it around, but there was a lot of interest from VCs, he said in a phone interview with Reuters after the announcement of the funding on Monday. The company was started in April 2009, and the product which was launched in January 2010, can currently be used only by people who have received a special invitation.

D'Angelo declined to comment on the financial terms of the deal, but said the funding will help Quora hire more staff and focus on a wider set of technical challenges underlying the product - an online question and answer service based on people's social connections.

The proliferation of start-ups with Facebook veterans, and the investor interest in them, follows a time-tested Silicon Valley pattern in which tech superstars from Google Inc to Fairchild Semiconductor have spawned innovative start-up companies, said Nick Sturiale, a general partner at JAFCO Ventures.

Any entrepreneur spinning out of Facebook is going to get attention, said Sturiale. They're at the vanguard of how the Web is emerging.

Facebook, which counts 400 million active users and is the world's No. 1 Internet social network, has yet to announce any plans for an initial public offering -- the traditional payday that allows early company insiders to cash-out and move on to new projects.

But the active secondary market for Facebook shares -- including more than $100 million in officially-sanctioned stock purchases of employee shares by Facebook investor Digital Sky Technologies last year -- has allowed Facebook employees to decamp at an earlier stage, say some VCs.

We've seen loads of people leave Google and now we're seeing loads of people leave Facebook. Either because they're vested, or because they think the company's gotten too big, said Spark Capital's Todd Dagres.

Dagres said he's looking at several start-ups founded by ex-Facebook employees, but he notes that a Facebook connection is not enough.

You definitely pay attention if somebody is leaving Google or Facebook. But then you've got to make sure that they really have built a track record, that they didn't just work there, said Dagres.

A number of Facebook-related start-ups have already passed muster. Asana, whose founders include Facebook co-founder Dustin Moskovitz, raised $9 million in December from Benchmark Capital and Andreessen-Horowitz. Cloudera, which features former Facebook, Google, Yahoo Inc and Oracle Corp veterans on its management team, raised $11 million from Greylock Partners and Accel Partners in two separate rounds of funding last year.

Meanwhile, Path, a secretive project led by former Facebook employee Dave Morin and Shawn Fanning, the creator of music sharing service Napster, has piqued a lot of interest in tech circles though it's unclear if the company is looking to raise money.

Some entrepreneurs, like former Facebook director of international business development Net Jacobsson, say there's no overwhelming pressure to raise capital right away, thanks to the low cost with which Web start-ups can be created these days.

Jacobsson, who advised social gaming firm Crowdstar after leaving Facebook in May 2009, recently set up his own social game start-up dubbed PlayHopper. The game development is primarily taking place in China, he said, and the goal is to generate revenue as soon as the first game is released.

Several VC firms have contacted him to check-in on his new project and in some cases to inquire about investing in the company, said Jacobsson, who noted that he was still thinking over whether he needed to take money from outside investors.

When it comes to VCs, it's like a marriage, said Jacobsson. A marriage you can get out of, but it's very difficult to disconnect yourself from a bad VC marriage.

(Editing by Lincoln Feast)