The source of the information is an executive(s) at Facebook, which as a private company is fairly free to say just about whatever it likes with regard to acquisitions. And what they are doing is clearly playing Business Week to get the word out that they are very much for sale.
And I believe Carlo at Techdirt nailed it when he draws comparisons to the way Skype handled its PR prior to its acquisition by ebay: rumors, rumors and more rumors about very high acquisition prices, almost to see how much analysts and journalists could stomach before saying “ok, that’s just ridiculous”. For Skype, the price was $4.1 billion. For Facebook, they’re just seeing how people react to a $2 billion price tag.
The price, by the way, is high but not ridiculous yet. MySpace was sold for acquired by Fox for half a billion dollars last year and has grown significantly since then. Many people are now saying that Fox negotiated a very good deal for itself. And while Facebook is no where near the size of Myspace, it’s no wimp, either. 85%+ of all college students use it, and they are now moving aggresively into the high school market.
A note on alexa rankings for Facebook: Unless you are a member you cannot view content on the site, making the network much more valuable for members but much less likely to get the massive page views and search engine juice that Myspace sites can generate. It’s not a very fair comparison. The simple fact that just about every college student in the U.S. uses it suggests that it has massive value, perhaps even greater than Myspace in the long run.