Here's interesting turn of events in the auction of an unauthenticated Richard Diebenkorn abstract painting on eBay. Final bid was around $135,000, but subject to inspection. I guess shill bidding occurs at all levels!
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eBay Suspends Seller of Abstract Art Painting
Wed, May 10 04:32 PM EDT
SAN JOSE, Calif., May 10 /PRNewswire/

It has been brought to eBay's attention that there was a questionable bid placed on the "GREAT BIG Wild Abstract Art Painting" (Item #320408444).

eBay has reviewed the matter and concluded that the seller
placed a bid of $4,500 on his own item, using a different user
identity. This practice, known as shill bidding, can artificially drive
up the price of an item and is strictly against eBay's posted
policies.

The bid in question was well below the final sale price and may
not have materially affected the bidding. However, eBay's policy
in these circumstances is to void the results of the sale and
suspend the seller, which it has done. The high bidder has been
notified of the seller's rule violation and is released from any
further obligation, though the parties may, if they choose,
complete the transaction on their own.