Facebook is still neither successful or unsuccessful in my eyes. They have yet to turn a profit, but its not clear the company is going to fall off a cliff. They still have a ways to go.
I am concerned they are still raising tons of money and burning through it so quickly.
It gets massive number of page views, and is very popular, but business isn't a popularity contest. If you can't figure out how to make money, you're not a successful business.