Sony isn't that stupid. They would be committing suicide on the video game market. Not only would they be preventing rentals, but they would also be forcing anyone whose system was ruined to have to buy new games, and they would prevent people from playing their games on a friend's system. This is a marketing disaster, and it wouldn't even do much to prevent piracy, since people who copy those games could probably find a way around it anyway. They would just be pissing off all the law abiding citizens who get their games (who also happen to be the major source of their income).