you know, you criticize this move (and certainly rightfully so), but I can honestly see practical uses for such a method of DLC access.
Imagine if you will that GTA 4, Ballad of Gay Tony, and The Lost and the Damned all were release on a single blu-ray for the PS3. (So this is at a time like now, when all three games exist and can be bought and downloaded seperately.
Now, imagine that you can buy this blu-ray with all 3 games instantly playable for 40 dollars. This will satisfy many many people.
But now, imagine someone who didn't go out to buy a game, but passes by this collection of games and wants to be able to play just one of the three games that night, it doesn't have to be all 3. But 40 dollars is more than he has on him anyway. Well what if they sold a version with just GTA4 activated, but the other 2 games still on disc, instantly playable if you purchase the "dlc" which simply unlocks those parts of the disc. And to buy it this way only costs 20 dollars, and each seperate dlc game can then be later activated when the buy has more money on him for 10 dollars for each other game, and as soon as he purchases it, the game is unlocked instantly, no waiting for any big files to download.
This would increase sales of that collection of games I bet (I know the collection with all three games exists, but to have the version that I imagine with the unlockable other games also available for sale, would definitely boost overall sales).