Damn, that bites the big one. Especially when you realize it could happen to anyone whenever you're in a public place.
On the other hand, I admit a certain grudging admiration for professional pickpockets. They practice a form of thievery that's been around for centuries, if not millennia, and requires a high level of skill and manual dexterity. Hell, a lot of pickpockets are probably skilled and smart enough to make a good living doing honest work. They just like stealing.