I've noticed this happening to the pets I've sold. I'll see that they were purchased and I'll go check on them, and find that they were released. I obviously don't care that much, since I was selling the pet anyway, but why do people do that? Isn't it kind of a waste of money? Is there a method to the madness? These are usually pets I would've released anyway if they weren't purchased within a reasonable amount of time, and I'm assuming that's how most people do it...so why?

A lot of people do that as a way to clean up the large amount of pets being sold. A lot of the time if you have a pet up for sale under 1k gold, it'll get grabbed and released. It's just something a few people like to do. Some players hold contests or have little clubs based on the act of buying and releasing. *shrugs* it's a bit of a sylestia thing

Seems like a bad monetary strategy, but I guess it's just a game after all! :)

Well the people who do it are usually the ones with money to spend. ^^ And since they go for the 1g first, it doesn't exactly take up much money. Pocket change as far as they're concerned. :)