So I've read Doug's article and watched the video, and besides developing a little crush on the lady in the top left picture, I started to wonder whether I would be brave enough to do such a thing, or not. Short answer? Probably not.
See, I really love my cars. They usually are on the lower end of the used car scale but they were the best I could afford at that moment, and I do my best to keep them in good shape. A tiny scratch would haunt me almost forever, especially if it wasn't done by me. I only have liability (plus all things glass) so insurance wouldn't pay to get it removed, and I wouldn't be able to bring myself to have them actually for it, even if they offered to do so.
This brings me to my next problem (?). I am usually a nice guy, and try to help my friends wherever possible. After all, that's what friendship is for, I think. So if they approach me with a request that involves my car, I am always happy to chauffeur them around, and I have yet to say no to a request to borrow my car. But all them know me well enough to only ask when they really are in a pickle. They know that I sweat blood until I have the keys again. I just don't like it, and they know that.
TL;DR: I very seldomly let very close friends drive my car, but I prefer not to. How do you handle this kerfuffle, especially if you have a really nice car, and friends want to test it out?