Well its rife! due to years of civil war and corruption within the government. Forced evictions also have had an impact on the numbers of families living on the streets, and you see them everywhere. Most Westies (travelers, Volunteers and other Expats) give a few coins to beggars, or shout a street urchin a free meal. I always seem to be an arsh@le to most of these people because I don’t do this(I’ve had the odd filthy look as I tell a cute kid begging in a cafe to rack off). I prefer to try to be helpful to locals, to pay a little above the odds for services and products, but still within the reasonable price range (probably inflating prices 
).
I had a long conversation with a well meaning tourist after getting a filthy look from her. I explained that giving money is kind and helpful, but some say that the best way to help ease poverty in Cambodia and to develop a deep sense of satisfaction as well as getting to experience more of the “real” Cambodia may be through volunteering or donations to reputable charities operating in Cambodia either before, during or after her time here. (trying not to sound self righteous about the whole volunteering thing)
in saying that the whole business of helping the Cambodians is starting to grate on me. Since there are so many NGOs and charity organizations here, some people say that these good intentioned people are not actually helping the people in the long run. To be so dependant on foreign aid may have a negative effect on the people’s own sense of empowerment and in turn passively waiting for help and handouts. I am still trying to measure the effect of this one.
So in the mean time, where ever I go I try to make sure that the place is locally run and the money I spend is going to the people who need it most desperately and not wealthy foreign entities. Unfortunately between all the Chinese Koreans and other western expats its pretty hard to do this in Phnom Penh. but I’ll keep on trying.
