If dirt were edible then we wouldn't really need to worry about ever having to find food since it would always be all around us. Dirt's scary that way. Even when you don't want it around, it's there, bothering the crap out of you.
I, for one, wish lava were edible. It's safe to say almost anyone would look cool scarfing back molten rock. That's pretty much everything that I can think of that I wish were edible. Let's just forget the whole thing ever happened.