Google launched last year a payment system called Google Checkout, but eBay refused to accept it as an alternative for its own PayPal because Google didn't have a "substantial historical track record of providing safe and reliable financial and/or banking related services".
Two weeks ago, Google Checkout team tried to make an appearance at the eBay Live event to celebrate user choice and to convince eBay to accept Google Checkout as a payment method. But eBay is a major AdWords advertiser, so it decided to use its biggest weapon and dropped all the US ads from Google. The move was pretty unexpected and Google quickly canceled the event: "eBay Live attendees have plenty of activities to keep them busy this week in Boston, and we did not want to detract from that activity. After speaking with officials at eBay, we at Google agreed that it was better for us not to feature this event during the eBay Live conference."
After 10 days, eBay resumed the ad campaign, but not without proclaiming the independence from Google. "I will tell you it will be in a much more limited way than it was before. What we found is that we were not as dependent on AdWords as some people thought," said an eBay spokesman. New York Times reports that eBay will buy more ads from Google's competitors, including Yahoo and Microsoft. Hopefully they won't advertise for dead people, murderers or nuns.