Plenty of things go wrong everyday at companies like FB that people don't see from the outside. If tons of things go wrong, and FB fails (whatever that means), entrepreneurship is the biggest thing Zuckerberg will have left.
If you read my other comments carefully you will see that I think he is under enormous pressure to shoot the moon and stay there. I guess this comes down to personal taste, and if you want you can be in his position. I'm saying there's a better 'canonical example' than facebook as of today, for the parent comment I originally used to put after his or her ellipses.
