Once in a while I come across an auction for a chip or one of the other things I collect and notice that all of the bidders have a zero feedback. Personally I don't care what is being offered and I back off; my gut tells me it's shill bidding.

My neighbor who sells regularly on eBay tells me that it's common and not neccesarily shill bidding.

For my money, after close to 600 purchases on eBay and having been a member since 98?, I rarely see it and when I do I move along.