An ease-of-use measurement: the easyl

This is a half-baked idea, but as a designer, I've always thought there should be some scale of measurement for the ease-of-use of something. The two ends of the scale are pretty easy to define. At the far end is something that is simply impossible, such as backward time travel or a pain-free Windows experience. We'll call this 0. And the other end is something that is impossible to prevent from happening, like the sunrise or the hype surrounding any Apple event. This will be 10. The midpoint (5) would be for things that are of average ease-of-use, which is more difficult to define. I suppose it would be along the lines of using a standard can opener. "Using" computer viruses are somewhere around a 7 or 8 on the scale, whereas using your average cell phone is somewhere around a 2.

That's about as far as I've got so far, but I thought I'd throw it out there and see if anyone else had ideas on this, or pointers to similar thinking. I'm too lazy  to do the research myself, so I'm trying to crowdsource it here. :-)