Pretty massive I would expect. They're either setting themselves up to be the ideal bride for Google or Microsoft or they'll be a very long term presence in their own right, until the 'next big thing' comes along in social networks.
Google tried it with 'orkut', that didn't work out very well except for Brazil, chances are they'll go and do with Facebook what they did with Youtube, buy it to avoid someone else buying it.
Microsoft seems to have missed out on the user generated content almost completely, Facebook might be very attractive to them.
The payoff for FB investors/owners will likely be unlike anything else seen in the history of the net.
"Unlike anything else"? That's a grand claim. The net's seen some real craziness in the past.
I remember when AOL was valued at $166 billion. MSFT was around half a trillion dollars at one point. It's unlikely that Facebook will come even close.
Google tried it with 'orkut', that didn't work out very well except for Brazil, chances are they'll go and do with Facebook what they did with Youtube, buy it to avoid someone else buying it.
Microsoft seems to have missed out on the user generated content almost completely, Facebook might be very attractive to them.
The payoff for FB investors/owners will likely be unlike anything else seen in the history of the net.