You need to look at each auction. Some are not very reasonable, others allow you to win the auction, pay a refundable deposit and give you some many days to do your pre-buy...not much different than Trade-a-Plane that way and maybe better as at least there is consequences (negative feedback) if they renig on the sale.
Others (see my post on the pre-buy question) go with a "fresh annual" and find out the integrity of the annual and AP conducting it was suspect...not good, but that has nothing to do with ebay at all.
I would buy on ebay in a heartbeat if the terms of deposit and inspection were reasonable and it was the right plane.
