They're probably feeling some competitive pressure from social networks too, those people are less likely to list/sell things on ebay when they have half the local population on FB.
Loads of localities have a [[locality] stuff for sale] page on FB where people are listing things for free and getting things sold.
I do agree about Ebay's aff structure not being useful to some affiliates. I was dabbling with it for a site for a couple of months and there were $500 worth of sales, but after a month EPC went to 0... regardless of the fact clicks were leading to sales. Didn't see much point in pursuing it further.