User satisfaction is important, and that's what could end up busting Facebook at the bank.
The users are their commodity. If they are unsatisfied and stop using the service (which they will when the next big-splash social site opens), Facebook finds itself with less and less value to offer their customers.
Not concerning yourself with the users is a great model for a turn-and-burn, but not for sustaining a business. Zuckerberg comes off short sighted enough that he either doesn't get it, or doesn't care because he can cash out with a big sale before the critical event.