I like the idea a lot, but would like to throw something else in there: make the adventure non-system specific. In other words, not D&D.

One issue I see with this -- and it may not be an issue at all -- but, if the referee/GM/DM/Storyteller/guy-with-the-map has the details of the scenario no the map, what is he going to show the players? Wouldn't there need to be a map without, "Here is where the cyclops steps out of the cave behind the players and ambushes them," written on it?

Or, maybe it's a split image. Half of the image is the map, the other half is all the details. There won't be any "'X' marks the spot" on the map. But, if people are printing it out on 8.5"x11", that's going to be a small map no matter what scale it is...