I've been using ebay for several years now, and have only had a few bad experiences:
- Bought a VW decklid rack, which was supposed to be original, turned out to be repro and missing pieces. I hammered on the guy for weeks before I got my money back.
- Sold a sparc 5 to a guy in Denver, who insisted on me sending it COD. He never picked it up, so I was out the shipping and COD charges.
- Had a jackass from SE Asia outbid someone at the last on a Telfunken radio I was selling. This guy was a chronic 'bid for the hell of it' - at any one time, he'd have ~$100k worth of bids going.
- A few misrepresentations of parts, usually claims of NOS or near NOS, and I get something in the mail which doesn't look like the picture.
I don't buy much off of ebay anymore, not so much out of principle, but more because there hasn't been much I need or want that I didn't have other channels for obtaining.