I was going to start this one until I saw you had, Musica.
Yes, just something else for us to feel guilty about.
I think, as others have said, it partly depends on what they watch. I think it also depends on how they watch. I used to do my chores while ds watched when he was tiny, but I always had an ear out, so I could talk to him about the programme later (and I'm talking about before he learned to talk), and relate other things we did back to what he'd watched. We also used to switch tv off to do other things, whereas I knew one mum (of twins) who left it on all day, and the kids played around it. That meant they kept stopping and starting, never concentrating on one thing, neither the tv nor their toys (nor her, for that matter).
And it's alright suggesting no TV to bright, educated, relatively wealthy mums who will do something else to stimulate their little minds, but what about the underprivileged kids, who's alternative will be to sit in a corner looking at nothing, not being stimulated at all, because their parents don't know any better?
Oooops, starting to rant now