[strags]

I added some copy-protection to a Nintendo 64 game once. If the anti-piracy checks ever triggered, the game would do nothing at first - but after a few minutes, the frame-rate would ever-so-slowly start to get progressively worse and worse until it was unplayable. I'd like to think that I pissed at least a few people off.

[stordoff]

If you're going to do that sort of piracy check, you have to be absolutely certain that it'll never trigger on a genuine copy. Red Alert 2 had a similar idea - about 60 seconds in to a game, all of your units will explode and the game ends - but it will sometimes trigger on legitimate copies of the game (usually due to mods, but I've had it happen on a clean install as well).