In the most extreme case, yes, there is such a thing as too much water. I remember there was news about someone who died from drinking a lot (really a lot!) of water and it flushed out the salt and minerals from her body or something like that but that's drinking a really insane amount of water though...there's a list of people who died from drinking too much water in the wiki page for water intoxication
. Too much of anything is bad in general.
I think most of those worrying about drinking too much water here are just afraid of water weight causing a higher number on the scale.