Within an hour of landing in Barcelona, I was pickpocketed by a pretty well-dressed gentleman who was so skilled at his profession that, on the shuttle from Terminal 2 to the train, he unzipped the wallet hanging across my chest at my side and extracted my ATM card and the 100 Euro I'd just taken out of the ATM machine. I felt nothing physically, but I did have a little spidey sense thing happen so I looked over at him -- he just stared right back at me. I didn't notice the wallet unzipped until after getting off the bus. It was not a crowded bus; there was a lot of space between people and I'm surprised no one else saw this happen either. Or maybe they did and didn't say anything. Or maybe he had some associates standing around him.
I guess by interrupting him I got to keep the rest of my credit cards, passport, and US dollars. Could've been a lot worse.
I was aware of the pickpocketing risks here, but I hadn't even arrived in the city yet. Be careful out there!