Through a third-party, retailing giant Walmart sponsors a white supremacist's blog that describes a desire for presidential candidate Barack Obama to be "tied up, gang raped, and have his neck cut" as "what we're all thinking." Walmart recently changed its logo and began touting its "green" initiatives in order to revamp its brand image. Guess one of Walmart's many ad agencies —Mediavest, Martin Agency, or perhaps Tribal DDB — didn't get the memo.

We've got a call into Walmart, but our guess is that through ad network LinkShare's affiliate marking program, hundreds if not thousands of Web site publishers put Walmart banner ads on their sites in hopes of referring shoppers and earning a slice of revenue from whatever they buy on Walmart.om. It would be very difficult to thoroughly vet each publisher. But if there's ever been a need for a clear example as to why Madison Avenue interactive agencies do not trust their clients to ad networks that claim extensive reach above all else, there is no more. Update: A Wal-Mart flack has gotten back to say: "We are investigating this matter and take it very seriously. This site used our banners without our authorization and we are working to have them immediately removed."