I have just replied to a thread about using Ebay listings to link to your own website over in the Promotion & Marketing forum that reminded me of something I have been wondering about. Before I start, I am cynical and jaded enough already

and I suspect strongly the answer to my question will be no, however:
- We all know that for many search terms, Ebay listings come right to the top as a result of Ebay's huge presence on the web.
- Many listings contain a legitimate link to an external site. Do these links help at all with the search performance of these external sites? In a normal situation they would help, but I wonder if Google & co have done something to prevent this - after all it would be all too easily abused....
Does anyone have any experience/knowledge to put this theory to rest?