I know its for charity and all, but jeez. Note, some of those pictures may not be work appropriate.
I'm all for runs with themes, entertainment, and breaking the mold, but there's no way in hell I would run in my underwear. First, while I may be an excellent distance runner, I don't have the body of a Greek God. Second, after a few miles, that underwear is going to be a little sweaty. And third, some times things 'rise' if you get my meaning.