With Facebook finally filing its IPO, the world of venture capital is about to see a new returns record, with Accel Partners expected to reap a vast money multiple on its $12.7m investment.

The Silicon Valley based VC first invested in the social networking giant back in 2005, when Facebook was only just beginning to branch out of its US university roots. With a $12.7m investment from Accel - and a further personal investment from partner Jim Breyer who sits on the board - Facebook has today grown into the biggest Internet phenomenon in recent history, with a reported 800 million users worldwide.

Accel's returns are set to reach similarly vast proportions: with its stake now valued at around $9bn, the VC's money multiple stands at around 700x. Breyer stands to make around $500m personally.

The deal dwarfs much of what has come before it. Even extremely successful exits such as Bessemer Venture Partners' sale of Skype - which netted a 150x return - seem somewhat small in comparison to the major feat achieved with Facebook.

However, some have cast doubt on the huge valuation of the social networking site, which is expecting to float for more than a number of well-established global companies. The firm has seen impressive revenue growth, climbing to around $3.7bn this year from just $52m in 2006, and generates net profits of around $1bn. However, it is doubtful whether Facebook can continue to see revenue grow at such a rapid pace. Though the site is expected to reach 1bn users this year - one seventh of the world's entire population - there are questions regarding how well its model serves the advertisers which it relies on. Clickthrough rates on adverts are extremely low, at around 0.04%, compared to Google's 8%, or rival MySpace's 0.1%.

Despite these concerns, Facebook's IPO is going to be one of the biggest events the venture capital community has seen for some time. Champagne bottles will no doubt be popping at the offices of Accel Partners, and the capital returned to its institutional investors should help fund the next wave of innovation from upcoming entrepreneurs.