It is hailed as the most important stock market event of the decade.

Rumours of Facebook's highly anticipated IPO filing on Wednesday have excited stock watchers around the world as the Palo Alto, Calif.-based company moves to raise as much as $10 billion - valuing the company at a staggering $100 billion.

But according to one analyst, tech rival Google could be about to rain on the social network's parade as its own offering, Google+, prepares to breach the critical 100 million-member mark on the same day.

Self-styled Google+ statistician Paul Allen is predicting that by Wednesday evening the search giant's fledgling social network will have 100.8 million users, as it continues to grow at an unofficial rate of 750 thousand users per day.

Allen goes on to predict that by the end of the year Google+ will have 'at least' 400 million users- around half of Facebook's 800 million active members.

Allen's predictions are based on his own calculations, and backed by official Google growth rates released last month.

In a press release sent to investors on January 19, Google CEO Larry Page said: Full year revenue was up 29%, and our quarterly revenue blew past the $10 billion mark for the first time.

I am super excited about the growth of Android, Gmail, and Google+, which now has 90 million users globally - well over double what I announced just three months ago.

I'm very excited about what we can do in 2012 - there are tremendous opportunities to help users and grow our business.

Allen, who founded Ancestory.com, uses his own innovative method to come to the 100 million figure.

His team track a list of unusual U.S. surnames, recording how many of those mention over a given period that they have signed up to Google+.

He then extrapolates this number to get reach a guestimate of how many new members the site has gained.

In the past Allen's guestimates have proven extremely close to official figures released by Google just days later.

Wednesday's highly anticipated Facebook filing with the Securities and Exchange Commission will reveal how much it intends to raise from the stock market, what it plans to do with the money and details on the company's financial performance and future growth prospects.

A stock usually starts trading three to four months after the filing.

Around the nation, regular investors and IPO watchers are anticipating some kind of twist - perhaps a provision for the 800 million users of Facebook, a company that promotes itself as all about personal connections, to get in on the action.