Vegetarian pets

I was recently surfing around vegetarian Web sites and came across some information on people who feed their pets a vegetarian diet. It's a concept that I've honestly never really considered and isn't something I would probably ever do. It would seem wrong of me to not give my cats any "say" in the matter and force them to become vegetarian when they clearly enjoy the flavor of meat. (Of course, that's rather a hypocritical feeling, since I didn't consult them first before I had them fixed!) And from what I've read, cats actually really need to eat meat because their bodies require certain nutrients that they can only get through meat. Though I also came across testimonials from people saying they feed their cats a vegetarian diet and they're totally healthy.

It seems that dogs, however, are omnivores and can more reasonably be given a vegetarian diet, although special care should be taken to make sure they're getting the proper nutrients.

I'm curious -- do any of you feed your pets a vegetarian diet? Would you ever do so? What do you think about the concept?