Technically, BioShock 2's downloadable content released before today. That's because it's on the disc. So, again, we're downloading an unlock. 2K says this was necessary to allow the entire player base to play multiplayer together.
The BioShock 2 community noted the downloads were 108K for the Xbox 360, 24K for the PC, so either 2K's achieved some insane results with compression technology or that's just a key to access code on the disc. A 2K community manager noticed "a bit of confusion" and stepped in "to clear things up for you". Here is the reasoning:
The way our engine and game structure works is that people need to have the exact same content for people to play together. One of the challenges with post launch content for MP is that it can split the player base, and we want to avoid that whenever possible. For this content, creating the DLC package the way we did allowed for us to not split the player base – so whether you purchase the new content or not, you can still play with your friends.
So if anything, this type of DLC delivery not only isn't going away, it's now offered with a bulletproof justification. You want to own all the code on the disc, well, do you really want to split the player-base? It's like putting kids in the middle of a divorce.