Here's some great info. about how pickpockets work.  Lean how to keep your wallet!  Guys, you can be robbed, too.  Women aren't the only ones these crooks are after.  One winter a couple of years ago while standing in a packed subway car, a pickpocket directly behind me slipped his hand into my coat pocket.  I elbowed him without turning around--I wanted to avoid a confrontation--beat at his own game, he immediately stopped!

I carry my wallet in my purse, which I carry in a messenger bag, so nobody is touching my money without me knowing about it!