I have a rather simple attitude to this. Those who are going to pirate won't pay for the game regardless whether the pirate version is available or not. Just don't make lives harder for the ones that are buying the games.
I am a fan of the Blizzard LAN solution and Introversion anti-piracy measures.
Blizzard (at least during Starcraft and Diablo I) had an option to install a cut down version of the game that could run without the CD and compatible with the full game's network games (IIRC). This was mainly for users who wanted to try the game.
Introversion used standard CD keys and Amiga style book codes to deal with copies but as an added measure to reduce the possibility of finding a pirated copy, they flooded the P2P networks of demos of the game that look/named like the full game. The idea was to frustrate pirates who were trying to find the game to download and as an added bonus, an 'innocent' user (one who doesn't know they are doing anything wrong) will be playing a demo instead which has details on where to get the full game from.