I'm may be the only person on the fence about dogs, and this is why. Every time I've ever owned a dog, I get the one that turns out to be completely untrainable, shits and pisses in the house, and never learns its own name. I spent the first three years of my dog's life trying to teach it to roll over. It NEVER learned how to do it. Whenever I get a treat out, my dog loses it's mind and reverts to the only method it knows to get that treat out of my hand: perform all the tricks she knows in the rapid-fire succession, concluding with a grand finale of laying on the ground, exhausted and out of breath. We now refer to that last one as "playing dead" and it's officially a trick. Basically, I need an animal that will just sit still for three hours while I lose all sense of reality on Stumbleupon.com.
Cat's I can get on board with. But that's a post for another day.