The thing is though, if the number gets high enough, let's say 95% of people just copy the game (not unlikely in the age of torrents) and only 5% purchase it - might not be enough to fund a AAA game, whose budgets now run in the 100s of millions of dollars, and, at $70/pop, need about 6-10 million purchases to make up for the flops that will also occur.
The real problem, is that if it's _really_ easy to copy, and the company puts in no attempts to prevent this, then a lot of the people who would have purchased the game, don't bother and just download off the torrents.
Tough balancing act. I don't know what the answer is.