Shamus Young, the fellow who did DM of the Rings, has an excellent post on games requiring online activation, which is a surprisingly high percentage of newly-released high-budget games. BioShock got a lot of bad press for this one, but Spore, for instance, has the same problem, and even the new game from the Penny Arcade guys uses it.

The problem is that if the company goes under, or just stops wanting to pay to support those game servers, you're screwed. You can't play your game any more, unless you go find a hacked version on BitTorrent. Not only is the company highly unlikely to do so -- if they go under, it would be distinctly illegal for them to do it. But hey, don't take my summary, go read Shamus Young.