We have a PS3 thread, a PSP thread (again), a DS thread, and we're on the third Wii thread.
But no X-Box 360 thread? Our coverage of the current systems is incomplete!
http://www.neogaf.com/forum/showthread.php?t=134598
When you download new stuff for your 360 games, you're not really downloading them; you're downloading a key. And it unlocks stuff you've already paid for. And it costs you more money to do so. Yes, the age of micro-transactions is here and people are happily paying out more for what they already own.
It sucks, but there's probably an end-user license agreement somewhere that mentions this, and no one ever bothered to check (who really reads those? I bet you could put just about anything in one, and no one would notice until weeks, or even months later).
On the other hand, with soaring development costs and lower profits, game developers may see this sort of action as the only way to recoup the millions they spent on the games. A company that maintains a healthy profit can survive for years during rough patches between releases.