|The 'Do It eBay' ads were Goodby's best-known work for the marketer.
EBay spokesman Chris Donlay declined to comment. "Our policy is not to comment on vendor relations," he said.
EBay's measured media spending in the U.S. peaked at $84.6 million in 2003 but last year dropped to $73.8 million, according to TNS Media Intelligence.
Agency co-chairman Jeff Goodby said the agency had tried a number of different approaches to help eBay fend off new competition from a myriad of dot-coms, including Overstock.com, and as other auction sites are offering lower fees to merchants who post their wares online.
Goodby Silverstein's most famous work was a series of ads themed "Do It eBay," which spoofed the Frank Sinatra classic "My Way."
For last year's holiday season, the auction house launched a sentimental campaign under the tagline "The power of all of us." The ads illustrated the idea that "People are good," one of eBay's cultural tenants. One sentimental spot showed a little boy playing on the beach who loses his toy boat, only to buy it back on eBay years later as an adult.
"I'm proud of all the work we did," Mr. Goodby said. "It was always successful, and I don't know what more we could have done."