Well, as N4S said, one of the best things you can do is find a bike somewhat close to you and go inspect it first. Ebay does give you some protection from scams, but not as much as really needed.
On a different note, I was coming in to post an update to my thread about the non-payer. I called him again on Friday and told him that I would sue for contract fulfillment, which he could do in one of two ways. One, he could fulfill his part by buying the bike, or two, he could pay the difference between his bid price and whatever I get for the bike. He said he'll buy the bike and will have the money on the 18th. I'll believe it when I see it, but it's more progress than I'd made so far.