According to Search Engine Land, eBay has been hit with a manual action penalty (A penalty which is usually a rankings demotion applied by a member of the Google webspam team).
Earlier this week the news was a buzz with speculation that eBay had been hit with the recent Google Panda algorithm update and whilst that’s still a possibility it has certainly received a manual action penalty according to SEL.
This is another high profile example of Google enforcing it’s Google Webmaster Guidelines and demonstrating no-one is too big to be slapped down a notch or two.