I did the same with minecraft ! Actually, it was a friend that brought a "cracked"(because it doesn't have much protection at all and it was pretty easy to do that yourself, no programming involved !) version at college and offered to all the class to copy it on their workstations.
It was back when the game was alpha. And one week after I bought it !
I also did this with : Mass Effect, Deus Ex, Stalker: Shadows of Chernobyl, Crysis, Company of Heroes, Fallout, Fallout 2, GTA IV, Red Faction, Space Quest, X-Com: UFO Defense, X-Com: Terror from the deep, X-Com: Apocalypse, Empire Earth, The sims, and the list goes on and on.
And for each of those, I bought the sequels as soon as they were out, not getting a copy from a friend first.