My folks fell foul of the "what's that mark on your shirt?" trick in Rome last year. Losses were tolerable but they were furious at falling for such an old routine.
I've not 'done' Rome but as with anywhere crowded, you can be unlucky. Then again, petty crime's endemic in Amsterdam but in three years, I'd just one inept pickpocket and one inept ATM-scammer. Rumbled them both, very satisfying!
My advice: 1. Wear a moneybelt - bumbags & shoulderbags are easy pickings for strap-slashers. 2. Be wary of anyone on the street who tries to get your attention. 3. Make sure you're insured. 4. Have a good weekend!