FWIW, I've bought quite a few software packages on eBay, but only stuff that's still sealed in the original box. I've bought Poser, Carrara and Photoshop that way, and was able to register them (at least, I went through the registration process, and didn't get any indication that the registration was invalid). I also tend to only buy software from people with a lot of positive reviews. So far I haven't been burned, but there's always tomorrow. Also, I keep out an eye for warez, and let eBay know about it (by sending the auction link to safeharbor@ebay.com). Ebay is very good about following up on complaints. You get a canned response when you send the message, and then you get a more personal response a day or so later, explaining what sort of action they took. As always, buyer beware.