I've probably said this a million times (well, maybe not as often as I talk about carrying hiking poles onto the plane), but in my experience the only way to protect yourself from pickpocketers is to not have anything in a place that they can access. Spaniards have a sixth sense about this, they are alert without being consciously alert because it's their milieu. If you live in a place where pickpocketing isn't a constant threat, no matter how hard you try, I don't think you are going to develop that sense. And when you lapse into careless oblivion, the pickpockets see it and pounce. Carry cards, money, passport under your clothes in a pouch, have cameras in the bottom of your pack, etc etc. The real benefit is that if all of your valuables are inaccessible, you don't have to worry. I once realized that a pickpocket had managed to open my purse on the Madrid metro, but since the only things in it were my eyeglasses, some Kleenex, chapstick and a few other trivial things, when I realized it, I just smiled and stuck out my tongue (maybe juvenile, but it gave me great pleasure). He got off at the next stop.