Scary stuff! Glad to hear that the person walked away with relatively few injuries.
My rule: No one else drives my car...period. I tell people that I'm the only one that's insured to drive it. My wife could drive it, but she has no interest. The seat rails have been removed and the seat is all the way back, so she couldn't reach the pedals anyway.
BTW - The other guy lent his car to a friends son? Why didn't he just hand the keys to stranger on the street?
Hindsight is 20/20...but what's the old adage..."common sense isn't all that common, is it?"