Any system that can run unsigned code is trivial to exploit to play pirated software, and no operating system that only ran signed code could be successful ...
In my opinion, software developers who are focused on producing comercial solutions to individuals (like videogame developers) need to consider that the PC is a platform which will always have high piracy and they need to consider a business model which doesn't require people to buy software.
Web application developers like Google and Facebook have created a business model where they sell a service (advertizements that target you) to a client (small to large companies) where you don't need to pay for anything for them to be successful. In contrast, Blizzard developed World of Warcraft and could easily give away the client application because the game is on their server and you have to pay to have access to it. A Hybrid model hasn't really been tried that I know of, but I would be interested to see how accepting people would be of a free FPS/TPS game that made its money by selling 15 to 30 second advertizements between matches ...
