Micorsoft has too much money that they just want to give away(sort of. They want you to try out their bing.com((used to be call live.com) for searching). They partner with eBay so that for certain products/keywords you search on bing.com, in the search result page, they show some links to eBay that offer some cashback. iPod

See this bing.com search result screenshot for sample cashback promotions circled in red. Be sure to check out the complete rule for restrictions.