Git is pretty close to ideal for the distributed model.

I think the real money is in figuring out a centralized model that doesn't suck. Explicitly locking things has certain advantages. Two people working on the same file at the same time is often cursed in some way even if a merge is technically possible. Especially if it's a binary asset. Someone is going to lose all of their work if we have a merge conflict on a png file. It would be much better to know up front that the file is locked by some other artist on the team.