No offense to Mark or Facebook, but they have a long standing reputation for ripping off other social network ideas. I'm sure he's just there to cherry pick the next round of features for facebook.
Never really understood how you can "ripoff" an idea. Technology or even design but an idea? I am not so sure. That is a problem, people need to stay clear from that notion. I agree with the cherry picking though, it would make sense. You are not going to turn a blind eye to the competition.