Reuters reports on Ebay's study showing that Google advertising doesn't work as well as it did.
"The conclusion: Incremental revenue from paid search was far smaller than expected because existing customers would have come to eBay regardless, whether directly or through othermarketing channels," eBay spokeswoman Johnna Hoff wrote in an email to Reuters on Tuesday.
The study highlights a potential problem for Google, which generated $46 billion in ad revenue last year, up from $38 billion in 2011.
Some leading e-commerce companies, such as eBay and Amazon.com Inc, that have traditionally been big buyers of Google paid search ads may not need the service as much anymore.
So what would you do if you were the account manager at Google, looking after only "mega brands" ?