Here is another link :-
6-8 8oz glasses a day is recommended.
I do remember that someone died from drinking too much water but that was a gross amount - cant find the link just now.
It seems that problems can occur from drinking large amounts in a short time. 10 litres in a few minutes is mentioned here :-
here is the link about the woman who died from drinking too much water (6.62 litres over a short period)