There was the story of the girl who took ectasy and drunk water until she died right? But that was (if I remember right) just because the bit of her brain, the bit I'd still remember if I did year 11 science again, that decides when to absorb/not absorb water wasn't functioning.
Surely, if you drink too much, you may feel a bit bloated, then urinate it out? If you body is working functioning properly, I can't see where the harm is in drinking more than your fair share; obviously if you feel discomfort, stop, but other than that, I can't see how drinking something as 'neutral' as water could be damaging.
Maybe someone could tell me otherwise, I'm quite interested as well actually.