That's basically what a pirated game is. A legitimate copy of game with a crack.
I think most people think of pirated games as being a copy of the game that
isn't yours. Sure, it was originally a legitimate copy of the game (for the person who originally uploaded it, assuming he or she paid for it), but it's not
your legitimate copy. That's what I meant when I said that I had pirated games in the past. If it makes it easier to understand, let me rephrase: "I've downloaded games illegally in the past, but most of my experience comes from using cracks with games I have purchased."
Now, the cracks aren't always good. However, bad cracks are always addressed within a day and a good crack is released. The "scene" has quality standards, so if a release is bad, it is either fixed or a replacement is released by another group. This is why I say that you need to have knowledge of piracy so you know what works and what doesn't. If you just download random crap off P2P, then yeah, there's a greater risk of things not working since many P2P releases aren't done by scene groups.
I know something of how "the scene" works, but what I was talking about was games that are deliberately programmed to sabotage copies of the game that are cracked. The only specific example I remember is X2, and I'm not sure if it was ever fixed. The effect it had was to harass the player by taking away his or her accomplishments gradually; this isn't something that would be obvious to crackers, so I don't know if they noticed. Thankfully Egosoft is one of the few developers that's smart enough to remove copy protection after a while, so it's a moot point now. But still, I wonder if it was ever successfully cracked?
I'm pretty sure that X2 wasn't the only game that did this. Like I said, I haven't cracked any recent games, so I'm not sure if this practice increased in popularity or not.