$10 billion for Facebook?

Facebook is a social networking site that was created in 2004 by Mark 
Zuckerberg (he was 20!), now it has around 47 million users.

In this article of the Guardian the journalist Bobbie Johnson explains us a 
summit between Rupert Murdoch and Chris DeWolfe (the founder of the
rival site MySpace - which Mr Murdoch's News Corporation bought two
years ago for $536m) about social networking sites.

With social networking sites, the only way to make money is through advertising.
Facebook is expected this year to bring in "just" $150m of revenues through
adverts and extras - it means only 3 $ per user this year.

Is Facebook really worth 10 billion US dollars?