Ebay is affected by this like any other ecom site. The changes in the algo greatly influence the quality of traffic they receive and their pages (product) visibility/position over the SERPS.
True, many users search ebay directly, BUT many (many) users find the products on the SERPS to begin with and only then go on to purchase. Thats how it used to work before anyway. Ebay, ecrater, bonanza, etc. ...same story with all lately. Dead, dead and dead.