Recently in Phnom Penh there has a been an increase in petty crime, it certainly feels that way. Having been in the country the last year or so and speaking to the locals and expats the same familiar story emerges from stories like these:
"I was in the market and two guys grabbed my purse and ran away no body even helped" or
"I was walking back home it was quite late but it was only 5 mins to my hotel, when I was robbed losing a small amount but also all my credit cards and passport".
Yes it seems that there has been a surge in theft in the Cambodian Capital. The reason for this could well be the economy. A lot of local people talk about the factories closing down and many jobs being lost. People do have to eat so they turn to easy pickings, tourists or even locals who have let there guard down. Or it could just be in Cambodia the police don't really enforce the law on the locals so some people see opportunistic theft as an easy way to make a quick buck!
Whatever the reason the city is much safer than it used to be, however one should be careful and think twice about walking home late at night or taking one of those motorbike taxis with a driver you don't know! They could take you anywhere.
This all being said Phnom Penh is a city and every major city has crime so the standard precautions apply to Phnom Penh as would do in any other city. Don't try to be too flash or walk about with your wallet in your back pocket or a fancy looking watch on your arm. If you must be walking around at night try to keep to the main roads but preferably take a tuk tuk from one place to another.