The recent TOS and security controversies haven't been good. Up until recently, excellent customer care has been a hallmark of YC companies. The Hellofax guys have been awesome, and incredibly responsive to feedback, as have the Parse guys. I hope when they get huge, things stay that way. It seems once these companies reach certain scale, though, other issues tend to limit this (see AirBnB). Of course customer service is an increasing challenge for all large companies, not just the ones that come from YC. But it's sad to see some of them lose their luster.

Sure DropBox is great for moving homework, but for anything where security is paramount, why take the risk? Security is one of those things that you screw up once, and X people will never forgive you. Would you trust your mission-critical files to a service that exposed them for four hours?