is eBay getting sued every time a counterfeit good is sold?
The problem with Amazon is that they seem not to take appropriate action. How can you not be held liable for printing books in an unauthorized fashion AND selling it from your warehouse?
Amazon sells almost 200bn of goods each year. Even if a tiny fraction of those are problematic and slip through the cracks, it'll seem like a lot to observers. Doubt they can get it down to zero, no system is perfect, and there are too many attackers trying to game the system.
It's a price to pay for all the benefits of the open platform model.
Ebay only allows 3rd parties to have a listing, much like craigslist.