Not too long ago, the existentialist question in the time of Facebook was: To join or not to join. Now, after the social networking site — the third largest grouping in the world, behind only the countries of China and India in population — filed for an initial public offering, the question is, well: To buy or not to buy Facebook stock.

It might be no exaggeration to say the world is split between those who back Facebook stock and those who don’t, quite similar to the divide between those who enthusiastically live life to the full on the social networking platform and those who shrink at its sight.

It is not a fundamentally sound investment, asserts Kenneth Wisnefski, an online marketing expert and founder-CEO of WebiMax, a search engine optimisation firm with a global footprint including Australia.

“In the first few days of trading, I expect the stock price will soar due to social-media hungry investors,” said Wisnefski, comparing it with the IPO of the professional networking firm LinkedIn. “However, once the market absorbs the emotions and begins to invest based on fundamentals, it is clear Facebook will not be a solid investment,” he added.

Wisnefski echoes the fears of many.

Facebook plans to sell shares worth $5 billion but has not said how many shares it will sell. Analysts value the company at between $75 billion and $100 billion.

Number-crunchers split

In 2011, Facebook raised $3.7 billion in revenue, a very healthy number for any startup. Even for a giant one like Facebook. But 85% of it comes from advertising — a matter of concern to Wisnefski.

“The company is not diversified enough to generate income from additional streams,” he pointed out. Besides, according to EMarketer, Facebook’s ad sales will slow down considerably — from 104% in 2011 to 58% in 2012 and 21% in 2013.

But there is another set of analysts wearing rose-tinted glasses that sees see nothing wrong with the set of numbers. To the contrary, these number-crunchers consider Facebook to be on par with tech giants such as Apple and Google when these companies went public.

Tristan Louis, the founder-CEO of Keepskot and an influential blogger, is one of them. He thinks it could be a steal.

“From a metrics standpoints, this company also appears to have a very strong business that compares favorably with other tech giants and the numbers bandied about in terms of valuation do not seem to be particularly outrageous when put in the greater context of the rest of the industry,” he concluded, after comparing Facebook with search giant Google, among others.

Facebook’s ad revenues are three times higher than Google’s at IPO and it is less dependent on ad revenue than Google — 85% versus 95%.  Louis, in fact, sets up a tantalising possibility that Facebook could have a market cap of up to $256 billion, if the market gives Mark Zuckerburg’s company the same valuations it gave to Google on the first day of trading. That, as you can tell, is more than double the currently estimated range of up to $100 billion for Facebook. You can read his analysis here.

At a valuation of about $100 billion, Facebook will be valued at a multiple of up to 27 times annual revenue, or up to 100 times earnings. That fares favorably with the valuations of Google or Apple at their IPOs. Google was valued at $23 billion at the time of its 2004 IPO, or 218 times earnings; and Apple was valued at $1.19 billion in 1980, at 102 times earnings.

Wisnefski, however, expresses doubt that Facebook will be able to match Google in terms of revenue growth. This is because he foresees increased competition coming from Google and Microsoft’s Bing in the social networking space and in the race for advertising dollars.

“Intense competition from Google and Bing pose serious threats to Facebook, as the infrastructure of Facebook is primarily focused on sharing images, checking status updates, and running apps,” he said. But “Google and Bing are well-diversified and are in a much stronger position to leverage ad-revenue in the long-term than Facebook,” he added.

Clearly, the final word hasn’t been said. As if to cash in on this debate, which will likely run all the way to the expected May IPO, an Irish bookmaker, Paddy Power, has begun taking bets on Facebook’s share price when it begins trading.

He is offering of odds of 7 to 2 that investors will pay between $25 and $34.99 to buy Facebook shares. To be sure. To be sure. Or not?

How much would your business be worth if you were Facebook? Take your annual revenue and multiply it by 27. Fair deal?