Well, I don't know if they actually did get around to putting Nintendogs in any pet stores, that's why I was asking. I could be wrong, but I thought someone at Nintendo had mentioned it in passing at some point. It would probably be part of their approach to get to non-gamers.
Non-gamers wouldn't walk into a store dedicated to video games, or go to that section/department in a larger/more diverse store. I had even heard of the idea of selling games in convenience stores, which would definitely get games more exposure than having a single series like Nintendogs in pet stores which only avid pet owners who constantly get new pets would be revisiting.
Back when the NES was the current hot console, I remember that several convenience stores had a game rental section. Now it seems like they don't, and any that still do probably just have a limited selection of a handful of hyped PS2 games and that would be it. If non-gamers would ever consider the Revolution, it might be a good idea to put them for sale in convenience stores, but it would have to be a fever-pitch momentum, otherwise it's probably not an easy thing to get stores to do.