In March 2012, eBay conducted a controlled trial to see what would happen if they shut off this “branded keyword advertising” by halting their purchases of search ads containing the word “ebay” on Microsoft and Yahoo search engines, while continuing to purchase search ads on Google as a control. There was no change in eBay sales via Yahoo and Bing, relative to those that came through Google — consumers simply substituted clicks on the unpaid search listing for the now-absent paid ones.
via Did eBay Just Prove That Paid Search Ads Don’t Work? – Ray Fisman – Harvard Business Review.
