Will it, won't it? If so, when? If not, why not? An entire cottage industry of speculation has built up around the public debut of Facebook, arguably Silicon Valley's hottest Internet company.

Mark Zuckerberg, Facebook's founder and chief executive, has remained mum on the social network's IPO plans, except to tell CBS's 60 Minutes in January that a 2008 IPO is highly unlikely.

That hasn't stopped bloggers and investors from interpreting Facebook's every move as preparation for an eventual public offering.

That Facebook has been steadily expanding its ranks -- it now employs 550 people, according to the company -- and recently hired a string of Google Inc executives, including Sheryl Sandberg, Google's former sales chief who is the new Facebook chief operating officer, has only fed the speculation.

A Facebook spokeswoman declined to comment.

Venture capitalists say the excitement around Facebook is warranted given the explosive growth in membership. The social network has more than tripled the number of active members to 70 million from about 20 million in April 2007.

Advertisers are attracted by the huge opportunity presented by social networks, where millions of people often post their interests and tastes on their online profiles. This online behavior allows advertisers to target their messages specifically to groups of people.

Social media is going to be mainstream, it's going to be ubiquitous, said Mayfield Fund managing director Navin Chaddha at the Reuters Global Technology, Media and Telecoms summit this week.

It's where people are going to hang out, he said, adding that the next Yahoo Inc or Google Inc is going to emerge from among the crop of these Web 2.0 start-ups.

WEB 2.0

That's the main reason why Web 2.0 companies -- called so because the Web-based programs they offer are more dynamic and interactive than dot-com era companies -- are getting large valuations.

Software giant Microsoft Corp took a $240 million stake in Facebook last year, valuing the four-year-old company at $15 billion.

That's slightly more than the $14.7 billion market value of HJ Heinz Co, according to Reuters data, but less than half that of Yahoo, whose market cap was $37.6 billion.

(Facebook) is not riding a crest, said Bob Davis, general partner at Highland Capital Partners. It is the crest in terms of what's taking place out there today.

Following the Facebook funding, in January Slide Inc -- a start-up that lets people create their own photo slide shows to put on their social network profiles -- received a $50 million round of funding, valuing the company at about $500 million.

Facebook's popularity is so immense that despite the lackluster IPO market, if they chose to go public tomorrow, they could, Davis said at the Reuters Summit.

But the overall market for initial public offerings remains daunting for most companies this year. Only five U.S. venture-capital backed companies went public in the first quarter of 2008, compared to 18 in the same period last year, according to data from the National Venture Capital Association, a trade group.

The founder of A Small World, the Facebook for high-fliers, told the Reuters Summit in Paris that market turbulence was also preventing it from making a public debut in Europe.

If the market was super-hot, we'd be considering a flotation, said founder and Chairman Erik Wachtmeiste.

Some venture capitalists said they've asked start-ups they fund to shore up cash for the next year or so, until the public markets open their wallets for their debuts.

But Facebook is in an enviable position, Highland's Davis said. It can afford to sit it out.

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