I was reading some reviews for Dead Man Walking, and a term struck me: "interactive novel". That's really what Dead Man Walking, and a few others (Homo Perfectus series, EndMaster games, etc) are. So I think this is a common enough phenomenon that it should be a distinct tag.
I also think it should be gated to storygames under a certain length. Say 50k words, because that's what NanoWrimo considers to be novel-length. This insures that the tag has a certain amount of prestige, and can only be applied to suitably long games.
Why does this benefit the site? It's because it's an excellent way of separating the wheat from the chaff. If you're looking for an epic, the easiest way would be a helpful tag indicating its length. Now, you can mouse over for the word-count, but that's not as eye-popping, and it's not as clear to new visitors as a tag would be.
