To be fair, SEGA is also guilty of doing stuff like this, so we can't leave 'em out. Remember when they charged something like 400 MSP to unlock everything on the original Sonic & SEGA All-Stars Racing?
Granted that on harder games it's would actually be a welcomed option (namely JRPGs), but something like this is kinda cheap.
Nevertheless, when we talk about games like Red Dead Redemption and Grand Theft Auto IV, it sucks that the achievements get blocked as a result of using cheats.
I do agree with you on that, Nameless 24. In theory, achievements are a great incentive to prolongue your enjoyment of the game, but in the back of my mind I think: "What the heck am I going to do with these gamerpoints?". There's something odd about having this controlled enviroment that we see in a lot of stuff like Xbox Live, iTunes, Steam,etc.