What would you do?

Do you have any acquaintances who are knowledgeable bidders on Ebay? If so, have one of then look at your data; that place is full of professional shill bidders.

Generally speaking, I think that cases like that should be handled by professionals in a professional manner. This means not in open audiophile forum with censorship as a bonus. But in any case, this is your choice. However, bid shilling is a serious violation. If you are going to disclose their names, your accusations will not have much weight unless you disclose your name as well.
You also said that you are not an audiophile, though you didn't say that you don't want to become one. Indeed you might be about to put yourself in uncomfortable position here. Is it worth it?

Inna, you are exactly correct again. This is all risk with no reward to me. The safe thing would be to stand by and do nothing. And no offense to any of you but I don't want to become an audiophile. In part, because this experience -- my first potential audiophile level product purchase -- turned me off so much. With that said, if anyone wants to cut me a deal on an Adcom GFA-555 I wouldn't be offended. Just saying.

But really, why does this have to be about me? I just have the information. Frankly I thought one of you would step up to the plate, take the information and do with it what you will. It is your community, not mine.

Put the evidence together and present it to whoever is in charge of the auction site. Let them determine if it's an issue or not.