With the economic crash and the epidemic of foreclosures, the homeless population of the USA is now estimated to be a million people. Violence against them is now so bad that Maryland and the District of Columbia have made attacks on the homeless into hate crimes. Similar legislation is pending in other states.
The most frequent perpetrators of these attacks are young men and teenage boys who sometimes videotape their assaults. The motivation appears to be nothing more than a low cost thrill. They know that this population is largely outside the law and will not go to the police. Attacks frequently end in murder. The situation is so bad in Las Vegas, with a large population of the newly homeless, that they now prefer to live underground in the flood tunnels under downtown.
Read about it here in the NY Times.