Frankly, we have no idea why people made us so paranoid going to Barcelona and Madrid this month. We are two guys who are city dwellers and have travelled the world from major cities to small towns to remote wildernesses. The hype associated with petit theft in Barc, however, actually got us very concerned.
What a waste of worry. At least in April when we visited. It was no different than any big city. We saw nothing especially disconcerting and found it unnecessary to take any different precautions than we ordinarily would. I carried a money clip and credit card in a front pants pocket that I kept a hand in when in the subway or crowded street or train station, etc. My husband kept a wallet in his front pocket. We left our passports in our hotel room safe along with everything else from our wallets that we wouldn't need while out. You do need ID on occasion so carrying a U.S. driver license was a good idea and perfectly acceptable everywhere ID was needed. We also carried a photocopy of our passports.
My camera bag was shoulder style so I could keep it under my arm in crowds. The zippers clipped shut in a way that no one could open them without me knowing. I was made so paranoid that I bought a PacSafe bag that is kind of theft proof so long as you keep it closed and hold on to it. My husband had a similar PacSafe bag but not for cameras.
In the end, despite going all over Barcelona and Madrid at all hours, no one seriously hassled us on the street, metro, busses, restaurants, markets... Maybe it is being from NYC and projecting something, or maybe it was being two guys, or maybe it was just not as bad as everyone says. Did people approach us sometimes? Yes--beggars, restaurant promotors, nightlife promotors, etc. I'd mumble something like "no gracias" and just keep walking. That was it. If a street or path was empty of people, we avoided it since we weren't familiar enough with areas to know which were safe and which we should be more concerned about. I'd do that in any city.
Does it get worse in summer? Are women targeted more because they carry pocket books? Are less experienced travellers more obvious targets because they leave bags open or loose track of them or get distracted staring at a pretty building or don't know how to respond to a ridiculous ruse? I don't know. But for anyone getting nervous prior to a trip, RELAX! Just take the precautions you would in any city.