It seems that for whatever reason, much of these reversed trades are spawning from hackers logging into people's accounts and giving away all their pets. It happened to me just yesterday, and now I'm in C$ debt. In line with this appears to be a huge influx of users quitting, and while I'd like to think they really are just sending their stuff off to better homes out of the goodness of their hearts, I've grown a bit cynical watching this whole situation unfold over the last few days or so.
My suggestions is that new posts in "CS Free Adoptions" be temporarily locked until things settle down and site security is improved.
P.S. Change your passwords, people! If your using the same keyboard smash across every game you play, your account is at increased risk of being compromised, and nobody wants that.