Alan Shutko
Explorer
If the item is a paperback book or a game cartridge, the publisher doesn't support the activity, but it happens because there's no practical way to discourage it. So, we do it anyway, and get used to the practice.
Actually, publishers can't stop it because legally, they can't. Book publishers tried to argue that they were merely licensing the material, but that argument was denied in 1908 by the US Supreme Court. Application of the First Sale Doctrine for software has had a varied history and it does not appear to have been settled whether EULAs can restrict you from transferring licenses.
For a very interesting recent development, ReDigi offers a market where you can sell "used iTunes tracks" to other users. They're being sued by Capitol Records, but Google is asking to file an amicus brief arguing that copyright should treat mp3s as material objects (in which case, first sale doctrine applies) or not (in which case, copyright does not give a distribution right for copies and phono records).
If nothing else, watching all this unfold has taught me that life is not as simple as conventional wisdom and EULAs purport to make it.