This is some cogent research however there are some important points to remember:
- Ebay is a huge and well known brand so these results do not apply to everyone
- Ebay’s key campaign metric is sales online – this is not true for every brand
- The test switched off search on Bing and Yahoo, but retained coverage on Google which has the largest market share and performance significantly varies between engines
- PPC allows more rapiditity and flexibility for advertisers who have many offers or new landing pages to switch around regularly. SEO takes more time to optimise for these items.