I used to pirate pretty much everything, I guess this changed for 3 reasons.
As games started to move more and more online I wanted to play them so I forked out the cash.
Secondly Steam has made it much easier for me to purchase a game download and play, there is no more needing to search for patches find cracks for those patches etc etc!
Most importantly as I started being able to afford games with out needing to choose between my drinking/food money (cause as we know beer is bread), Eventually I ended up purchasing all my games.
Think the last thing I pirated was black ops, thank goodness I did, it was annoying, put down the game 30 mins in and went back to bad company 2. If I did like it I would have purchased it because I would have wanted to play it online.