I hate them because I love them so much.

BF3 has a pile and unlike previous incantations most are not simply about putting time in, they are about using specific gear. COD has even more specific achievements (unlocks, perks, rewards, goals, whatever). I just finished Mark of the Ninja (VERY GOOD btw) and will replay it because I didn't have some stuff figured out when I played the first time.

My biggest time sink has been ME3 Multiplayer. The unlocks there are massive. You unlock cool new weapons, awesome new character types, plus piles of other perks. It is highly addictive which when combined with a good game gives it even more of a hold on my gaming time. They also have a second layer of more traditional achievements which basically are displayed for everyone as "game cred" - as much as a video game can do that.

But yeah, I LOVE (and hate) them. They keep me playing way past when I should. For me though they do that mostly with multiplayer games because very rarely will I replay a single player game (MotN being an exception because it isn't a massive time commitment and I really want to see if I can do some of these things).

Simon