Microsoft's recent purchase of 1.6 per cent of Facebook for $240 million has got many people worried about the future of social networking and the sanity of Microsoft.

Let's face it; a 1.6 per cent share of any company will just about get you an invite to their Christmas party, but very little control over their affairs.

Microsoft has effectively valued Facebook at $15 billion, which is a lot for a company that takes no fee from its members and could be wiped off the face of the internet in a matter of weeks when people get bored of poking each other.

So why did the Redmond giant part with the cash and, more interestingly, why did the Web 2.0 darling risk its popularity by associating itself with the allegedly evil empire? The answer is simple: advertising.

Facebook needs to move to what is known as the monetisation phase of it business plan, which usually means selling advertising space. As part of the deal, Facebook will deploy the Microsoft advertising platform and share any revenue it generates.

Microsoft is desperate to get into the advertising business and block Google's threat to take over the virtual world one click at a time.

Google nabbed the other Web 2.0 hipster, YouTube, earlier this year so it's one-all in the content stakes so far.

But has Microsoft got its sums wrong? There are a reported 50 million people on Facebook, making each member worth $300 to Microsoft. So next time you login to Facebook, why not ask chief executive Mark Zuckerberg, who is everyone's friend, for your cut.

How many of the 50 million still login regularly is hard to determine. How many will vote with their feet the moment ads start getting in the way of their online fun is also debatable. Social networkers are notoriously fickle, but despite its mainstream popularity, Facebook still has that cool, underground feel of socialism. However, one whiff of Microsoft or the distasteful odour of capitalism that is advertising could see a mass exodus.

Although it seems leaving Facebook is quite difficult.

Technology tabloid website, The Register, has been documenting what it is calling the 'Hotel California Effect'. It seems even if you deactivate your account your data is kept forever and you can still be invited to events via email. It seems that with Facebook, 'you can check out anytime you like, but you can never leave'.

You see, we should really pay more attention to those terms and conditions when signing up to a free website.

A common theme running through the many attempts to define Web 2.0 is one of social revolution and the creation of powerful communities that can now keep corporations honest by harnessing collective consumer opinion.

But perhaps we naively thought the founders of a social networking site were idealistic leaders of a rebel cause. It turns out they might just have been creating huge personal data farms to sell into targeted marketing.

* Chris is head of digital at WAA (www.waa.co.uk). Email chris.tomlinson@waa.co.uk.