Why? In the end your disk is basically just an install disk and your game gets launched by Steam and tied to a Steam account anyways? Steam is a lot better than other things like Starforce or SecuROM, as the only requirement is that Steam is running with a username logged in (Online or Offline mode) with he game you're trying to play.
Regardless of a physical copy or virtual copy, you still have Steam to "deal" (term used very loosely, as Steam is pretty great) with. In fact, I'll likely just go to my steam account with the boxed version, toss in the CD key and go off that way.
Kev: It's true, but I tend to enjoy (most of the time) just playing random public games. There are a percentage of knobs that are like "HAH U DIED LUL", but then for every one of them, there's an equal amount of innocent players who are genuinely trying to play.