I think if you replace it by watching TV/video on a computer then yeah it's the same thing (minus the cable bill) but if you are reading, writing, posting, whatever online then it's a lot better, more mind stimulating.
One big reason I want to get rid of it too is I have a 17 month old son. Currently he watches zero TV, no movies, no nothing. Other kids around his age seem to be quickly addicted to Spongebob, Cars, all these Disney movies. I watch our friends plop them down in front of the TV like it's a babysitter. Our son is so smart and interactive. He is already saying 2 word phrases, knows body parts, baby sign language, he jokes with people, he is adventurous, social, builds mega blocks, knows some shapes, etc. I feel like if he starts on TV it will rot his brain.
Growing up we were friends with a hippy/dual college professor family with 4 kids that had no TV's. Those kids read big thick books constantly. Our friend, Ryan, he always had a 4" thick paperback dragon or imagination novel in his back pocket. Those kids all got straight A's, 2 of the 4 went to Ivy League schools and graduated with honors and all 4 are doing great things in life. Obviously genetics is a big part but no TV and lot's of reading and playing can't hurt. They used to play board games in the evening as a family. They weren't the coolest kids in school but they weren't picked on either.