The only tangible I can sense with content (code, media, etc) is how it's provided, and that means that service is the entirety of our business. Zynga isn't producing original content, but they are producing a valuable service. Do I think it's ethical? No way. But should it be illegal? Not unless you want to limit how we can use data.
In this case, what Zynga is doing is copying game design. And in a perfect world...I think it should be perfectly legal to copy game design, because the alternative is software patents, and do I really need to spell out why that sucks?
But it's still ethically and morally wrong, and we should name and shame Zynga, their developers, and their enablers. How about a boycott of Amazon until they yank Zynga's hosting? (And yes, I realize their isn't the slightest hope of such a thing...)
Call me naive, but I would at least like to believe that these types of practices cannot sustain a business forver, and eventually a player who does things the right way will win out.