eBay study dismisses value of advertising on Google "Removal of these advertisements simply raised the prominence of the eBay natural search result," according to the report presented at an economics conference at Stanford University. "Shutting paid search advertisements closed one costly path to a firm's website but diverted traffic to the next easiest path (natural search), which is free to the advertiser," continued the report by eBay executives Thomas Blake, Chris Nosko, and Steve Tadelis. The study highlights a potential problem for Google, which generated $46bn (£30.1bn) in ad revenue last year, up from $38bn in 2011. Some leading e-commerce companies, such as eBay and Amazon, that have traditionally been big buyers of Google paid search adverts may find that they do not need the service as much anymore. "This has to be a major concern for Google," according Oren Etzioni, an online search expert at the University of Washington and co-founder of shopping service Decide.com. "Strong brands like eBay, Amazon, and others need Google less and less as they have established a loyal online following," he told Reuters. The eBay study validates this common-sense conclusion. Even at the far smaller Decide.com, we've found that buying ads on Google was not cost effective. The report did not suggest any change in plans for the way eBay carries out search engine advertising. Google said that its own research suggested there was a significant increase in clicks as a result of search advertising. But a company representative added: "Since outcomes differ so much among advertisers and are influenced by many different factors, we encourage advertisers to experiment with their own campaigns."