IMO this company is here to stay. They are profitable and have convinced people that selling their non identifying personal info isn't a big deal. None of my friends really care that FB uses their info to make a profit. Of course they all cleaned up their profiles since they first got on, but that was to be expected. Their were no social standards for this realm yet. People needed to discover what its role in society would be and how their representation in this field would affect their life as a whole. Now that a lot of those questions have been answered users can more intelligently post on and use FB. This gives them some comfort in knowing FB uses their data for a profit. FB has large profit margins and a vast amount of data on the social world. It is a gold mine for data and users are going to continue to use it for the foreseeable future. IMO it's worth a pretty penny. 50 billion is just a number. It may not be worth that much today, but I'd put money on it being worth more than that in ten years.
Another thing to consider is the number of individual, fairly often users. That number is much less than the often quoted 600 million. One person can have multiple sign ups (just like here) and a fairly big number of users might use it only occasionally (just like here). Or they might not share much personal data. I would say the number of daily (or fairly often) users is probably 1/5th of the all accounts. It is still a huge number, but considering that 2/3rd of the accounts are NOT from the USA, it can be "only" 30 million Americans. I am not sure there is huge advertising value of users from Albania and such. They are still working on tapping the Chinese people and as it was mentioned in the CNBC Facebook special, China already has its own social networking sites... By the way the current number what they mentioned was 1 million new sign up per week. Doesn't seem to be slowing down, just yet...
It isn't worth 50 billion right now, but we have to see how it grows and develops. One day everyone in the world might be using Facebook.
Facebook advertises that 50% of its user base visits at least once a day. The majority of college aged and younger live on it. They also say 70% of Americans have an account. Sounds like they have a lot of influence.
I don't think everyone in the world will use Facebook some day, like some tribes living in the jungle.