I've bought quite a few prints on eBay. I'm drawn to work that is different from what I do, or am able to do, stylistically. This includes nudes (I have quite a few of Ray Bidegain's exquisite pt/pd prints), surreal work and architecture. My main criterion is that the print evoke a strong emotional response. Whether it's conventionally "beautiful" is irrelevant. If I buy it, it's beautiful to me.
Selling on eBay is the main outlet for a lot of very talented artists, including people who would never sell their work through the gallery channel, or any other channel. In my opinion, it would very unfair to say that an association with eBay cheapens an artist or his/her work.
I've also begun to trade prints with others on this forum and elsewhere, and find that even more rewarding than buying prints.