I really don't know the answer but personally I'd be more leery of the eBay toolbar than Auctiva...
http://www.tenebril.com/src/info.php?id=101505050
http://www.fbmsoftware.com/spyware-net/application/Ebay_Toolbar/
Although I don't know if it's really any worse than visiting eBay itself on a regular basis.