You never know what people do with used cards. I've made quite a few transactions on eBay directly dealing with technology and a rule of thumb I've stuck too is not to buy storage mediums. I don't buy used hard drives, used SSDs (these are like disposable napkins), or any other other sort of storage unless they're new or under warranty still.
Other hardware is a lot harder to burn out since it has no moving parts (relatively speaking). Warranties are nice, but I wouldn't worry about them. I would rely more on paypal and the seller offering returns on the items. If the seller sends you a box of rocks it's pretty easy to get your money back through eBay, just the same as if they send you something that isn't as advertised.
eBay is really about time/money ratios. How much is your time really worth? eBay transactions can go either really good or sometimes really bad, so it's a good idea to think of it like that. It's always a gamble.
I agree with that for the most part. I don't buy used parts for myself on eBay either unless it has either warranty or a strong stated return policy. I do buy stuff on Craigslist on occasion though. Mostly because it's possible to see what you're buying and who you're buying from beforehand. I bought my card from a guy who turned out to be an enthusiast as well and he seemed on the level. He had 2 of these but was selling both to get a 6990. Of course one still has to be very careful when buying used even on Cl.
Sync: 6950s are no longer unlockable. It was just the first run of them that were.
Even the reference 2gb design is not unlockable anymore? I thought all reference cards were.