The article suggests it could have been a coincidence, but I doubt it...
As thousands of eBay’s largest sellers prepared to gather in Boston for their annual eBay-sponsored convention and party this week, Google, the Internet search and advertising giant, decided it would be a good idea to invite those sellers to its own party. Not just any party, either, but one to promote Google Checkout, a payment system that competes with the eBay-owned PayPal and which eBay has banned from its auctions.
“Let Freedom Ring,” read the invitation on an official Google blog. And in classic Google style, it promised “free food, free drinks, free live music — even free massages.”
That did not sit well with eBay, and early Wednesday the IDG News Service reported that eBay had decided to drop all the ads it places on Google’s search engine. EBay is the largest buyer of Google search ads, according to Nielsen/NetRatings.
(See the article for the rest of the story)