think late game with a gold 4 generator
even at 32g per bucket that's 1 stack and you a inf source and 2 buckets.
it wouldn't help people camped up however as it would assist people diving into their base. also if you were to get knocked off it was likely with a bow in which case they'll just shoot you again, if not they can just block up the water and your dead anyway. as zRinne say tnt would also become useless if someone had water on an important bridge/fort
also fall damage would be practically gone from clutch bucketing when you fall.