DLC can be a precarious thing for all types of games, but it can be utterly terrible for those that focus on multiplayer and sharing the experience, tearing a rift in the community and causing a host of problems and issues that might push people away from the game, instead of drawing them in.
Major Nelson is no stranger to speaking his mind as part of his duties at Microsoft. DLC is a point of contention with many gamers, and he happens to agree that it isn't always a good idea. Particularly when it's paid. DLC, and Season Passes can be "really dangerous when it comes to multiplayer, because what happens is it fractures the community," he said during the latest Podcast Unlocked episode. "You have the maps, I don't have the maps, I didn't buy that map but you bought that map,' so when we all get together, 'Oh, you couldn't play the map."
It makes it difficult to have a coherent community that can actually enjoy the game together. And prohibiting those that already own the game from playing with their friends that own other parts that you don't have can potentially have the effect of diminishing the player-base completely. Free DLC, even if the content is small, can add significant value. A new map occasionally, new weapons, new skins. Those can bring people into the fold and keep them there, but making people pay for what might be considered (even though development time and cost of the items might be significant) trivial items can alienate users.
Single-player DLC is a different animal and is definitely a controversial topic among gamers. We don't want to continually shell out money for a game that we might not consider to be complete, yet the developers (and anyone who's made something can appreciate this) would like to be compensated for the work put into the new additon. Even modeling a new weapon isn't necessarily an easy chore. Time costs money, but we need to find a balance between overcharging and sustaining a business. That's not easy.