Originally Posted by jswinf
So the server would have to call it before (or pretty much simultaneous with) the returner strikes the ball, right? If the returner rips an outright winner and the server says, "Uh, that serve was a let" there's potential for abuse.
Yep. Best thing if you hear (or see) a service let is to call it immediately to minimize the likelihood of arguing over the timing of the call.