Originally Posted by Abecedary
I may be mistaken, but I believe that checking or verifying the validity of the works beforehand opens them up to considerably larger damages in the event that something ever does slip through. Also, as it is, they are working within the current legal framework (i.e., removal of infringing material after receiving a takedown notice). It makes perfect business sense to operate as they are now until such time as they're forced to add a verification department. Note also that this is exactly how YouTube and Scribd operate (or just about any site/company that allows mass uploading of user-created [or potentially infringing] content).
The main difference here is that Youtube does not sell their videos for profit, whereas Amazon does. Not sure if Scribd does, as I have never visited their site.