What makes you most suspicious of an eBay auction?

[36GoudeyMan]

.... when a seller of product X suddenly starts selling Ruth and Gehrig card about which they "know nothing" and swear someone said they were authentic and worth thousands, but they can't guarantee authenticity; or when the seller is new with little feedback (sorry, I know we all started that way, but probably not by selling T206 Wagners with a feedback of 3).

Basically, anything whereby the seller does not stand 100% behind the guaranteed authenticity of their card, with refund guarantees, and without feigned ignorance of or some BS story about the card's origin, worth, grade or value.

[Brendan]

Whenever the seller says he knows nothing about his cards and/or card collecting.

"I don't know anything about these cards or how to get them graded but my grandfather left them for me when he passed away. The bidder can decide for himself whether these are real or not."

Anything along these lines is clearly going to be some sort of reprint.

High end ungraded cards are another thing you've got to watch out for, but can be trickier because they often are real. Less feedback is important, too. I usually like to check the actual comments in his feedback because a lot of these guys aren't good buyers and that often translates to a bad seller.

[barrysloate]

The word "Wow" with exclamation points in the title. For example:

T206 Nattress with Five Creases.....WOW!!!!