Brekke launched Target's crime laboratories, five years ago, with the intention of fighting the "brick and mortar" storefront fences and warehouse repackaging operations that King Rogers had helped to uncover. But since then, Brekke says, the labs have increasingly been used to fight "e-fencing," the resale of stolen goods online through eBay, Craigslist, and other e-commerce sites, where thieves can operate with virtual anonymity.

That's part of the appeal of an online auction to thieves, retail experts say. Criminals can "e-fence" stolen goods with virtual anonymity and little risk of being tracked, compared with the face-to-face transaction of selling the merchandise to a pawn shop or from the back of a truck.

"It's throwing sand in the wind for us to try to investigate a case," Hummel said.

The seller-identity dilemma is one U.S. Rep. Bobby Scott aims to solve with proposed legislation known as the E-fencing Enforcement Act of 2008. The bill would require operators of online auction sites to keep and disclose the contact information of any "high volume" seller whose listed items match the description of stolen goods as identified in a police report.

Many online auction shoppers never stop to think that the seller with an alphanumeric name might actually be the same creep who in a different era hawked stolen goods in a seedy back alley. …

There is no national database for stolen property, … [and] law enforcement from Washington to the Mundelein Police Department say there's no way right now for a shopper to call up and check an item while the clock is ticking on an e-auction.

The Australian government thinks e-fencing is a big enough problem that it's looking into adopting such a system.