I meant prediction of the player's view, though, not other clients. Other clients can be interpolated fine, I can assume, without any protocol change or modification whatsoever, although to be accurate in being shot, their positions would have to be stored on the server over the last second or so, and then jump back in time or sommadat.
But thanks to all the posts in this thread I'm really understanding the concept now. I've also read a few articles and essays on the subject and feel confident that I can make a functional prediction system for my game, albeit with some changes to the protocol. Thanks, guys!