Speaking as someone who both buys and sells cameras on eBay, I think most of us sellers realize that foisting off junk will only last one or two times before no one is willing to buy from you. That's what the feedback section is for, (although I have had instances where far-east, volume sellers on eBay have manged to erase my bad feedback a day after I left it). I sell mostly Olympus and Mamiya cameras, brands that I worked with and have knowledge of. I sell Speedotron flash equipment for the same reason. I have a test pattern that I follow to determine if a piece is working and nothing makes it out the door without being checked.
And that is why I was upset over my "winning bid" on a NM camera arriving with a sticking shutter. That should, and would have been caught when it was tested by me. Cosmetics are one thing, function is primary and mandatory.