eBay is a popular shopping portal with affiliate program, not unlike many other popular sites, but there seems to be set of circumstances that Post Panda play havoc on the publishers sites. I'll try and explain as best I can.
Publishers linking to ebay often do so using popular wordpress based scripts that make it easy. A staple of these scripts is a redirect page along with nofollow on links to ebay.
I've heard it discussed that there is no reason to nofollow a link to a trusted site anymore and that redirecting just ads an extra step which is often just a way to avoid telling search engines you're linking to a site. Yes, there are other reasons a redirect can be useful such as geo-targeting and bot filtering, but to be honest that's not the reason many spammers do so.
eBay however is a different story because of their payout system. They have their own internal algorithm that, mysteriously, decides what a click is worth and eBay has said that bot clicks or clicks from the wrong countries can indeed lower your earnings. eBay affiliates are therefore smart to control access, and even to use the redirect page to swap out a NON affiliate link version to the same page, via use of a redirect page.
Now, if Google is looking down on affiliate redirecting and nofollow etc while eBay requires some link control, what's an affiliate to do? Darned if you link to what you're talking about and darned if you don't.
I know opinions vary but this is a case where a clear explanation that yes(or no) there are ramifications in place for using a redirect page and/or nofollow. The ebay payout system is unique, no other affiliate program decides what to pay per click like ebay does. In fact most affiliate programs simply filter bot clicks and such without penalizing their affiliates.