All the tourbooks and web sites warn that pick-pockets are rampant in Rome. They'll accost you on busses, on the subway, as you're waiting in line at the Colosseum, and as you walk through Termini. They're especially prevalent on bus routes 64 and 40, since those are heavily used by tourists. They cleverly work in pairs or groups, with one person distracting you while another picks your pocket. A crowded bus or subway train makes it easy since you're continuously getting bumped, so you won't even notice someone taking advantage of one of those bumps to pull your wallet out of your pocket. I've even read that they'll slash the bottom of your backpack with a knife and run off with the stuff that falls out the bottom. I suppose this is all true, but during my trips to Rome (admittedly, only 24 days of time), I never had an incident or saw one. However, I was careful to not advertise that I had anything expensive (kept it all in an unmarked backpack, not a "Canon" camera bag), I took my backpack off my back and carried it in front of me when I was in a situation I'd read warnings about, and I kept my passport and most of my money in a money belt under my clothes. I just kept cash for the next few hours and one credit card in my front, not back, pocket. Maybe those precautions were sufficient; maybe I was just lucky. I hope you're lucky, too.