Haha, this is a great thread to read before going to Barcelona for the first time on Monday!
I've heard of this, and as long as I don't wander out with all of my money - I'm not going to be
too annoyed if it goes. Apparently they're 'bloody good' so I will have to grudgingly admire their 'talent' and move on. I can't see me getting distracted by street performers - as I hate them anyway!
They are unlikely to be able to get into your socks or bra (may I suggest you wear at least one of these items of clothing - make sure they are decent socks with proper tall elasticated tops on) without you noticing without you being really fuckin arseholed.
Another one I've found useful is those money belts with the zips on the inside that look like normal belts, chaining everything to myself (but still keeping loose cash and at least one debit/credit card somewhere separate, and as a female wearing trousers with tight fastenable pockets that are completely concealed under a skirt or dress. Other stuff to look out for is stuff with zip-up pockets where the zip runs counter to what you expect, such as some outdoor gear you get, and shoes with easy to lift out and replace insoles.
Generally I am so much of a munter that I also aim that nothing should fall out even if a giant were to pick me up by the feet and shake me.
So far (touch wood) a combination of these methods have served me well.
Things I never ever tend to go about with in cities are loose open pockets, handbags, camera bags, etc. as these are bait as fuck if you want to get robbed or mugged.
The more valuable/irreplaceable the item is, the closer I try to keep it to my skin...most hotels (if you are lucky enough to afford one) will keep your passport in their safe, to avoid carrying it about with you.
I do own a handbag but it's just for makeup and toiletries, as it's basically a target on a string. I was gobsmacked when I found out my mum has been going into London for nights out for years with her keys, wallet, and phone in her handbag, I mean ffs!