If I was a coach, I'd ban it from my team altogether.. Nothing more than the prick you like like when you give the batsman an earful and he spanks you for four..
I'd love to see a team confront Kevin Pietersen with absolute silence.. No banter, no encouragement from the bowler, just steely silence and some damn good bowling.. I think that would freak him out..
I personally don't find any form of sledging acceptable in the slightest, but obviously you cant ban chat or anything from the game totally..