Haha this again, here's a thread about it.
http://www.bikeforums.net/showthread...=#post10798828

As AEO said, anyone with a 15mm wrench can steal your wheel; even a crescent wrench and your wheel is gone and a lot of people do not lock up their bolt-on wheels, they just lock the frame. Also, if you happen to have a flat on the road, you can't do anything unless you have your wrench with you.