Facebook is one of the most interesting company out of there. They went from few millions of users up to five hundred million in a couple of years. I forecast they break the billion by Q2 2012.
In addition, running the business is not as expensive as search. They need to store user profiles and a lot of images. Video is outsourced to youtube and realtime updates are not so expensive (what is the history they maintain?).
Anyway, running a business requires to make money. So here is my call: What business model do you suggest for facebook to make money?
Content ads never worked for search. Could it work for FB? Or what else?