I wouldn't mind if the DLC was actually cheap. For example, I know buying a further 4-5 maps on Call of Duty is worth my money to an extent because I'll get a lot of play out of them, however it shouldn't cost 1200 Xbox points (£8-10 I think). From what I've heard as well for the Black Ops maps, and probably with all maps in fact, is that they were created during the game's original development and simply weren't included in the game for one reason or another (didn't make the cut perhaps?), so to then later charge extra, and a fairly substantial amount in gaming context is just silly.
It seems now that every title has at least 2 or 3 DLCs, which generally add up to around £15+, some undoubtedly topping £25+. That's when it goes from somewhat 'acceptable' to just insulting.