Years ago, when you could still see bidder ID's and dig deeply into past auction results, I seriously thought about bidding on a very nice '51 Plymouth. I started researching the seller, and discovered that his cars always seemed to attract the same three bidders, and he was bidding up their stuff as well. I held off on bidding, and, lo and behold, the last $3,000.00 of bids were propelled by the same three people. An outsider got the car, and I really think it was a case of bid-running.
I even notified eBay, with detailed data that I had accumulated, and they did nothing about the seller, as usual.