"YouTube.com video prompts probe of LAPD":

An FBI investigation prompted by video footage of a man being punched repeatedly in the face by police has demonstrated anew the power of the Internet sensation of the year, YouTube.com.

In addition to being a monumental time-waster around the office, YouTube could also become a tool for keeping police honest, some say.

This week, a clip on the post-it-yourself video Web site triggered a police-brutality investigation by the FBI. The footage shows the Aug. 11 arrest of alleged gang member William Cardenas, 24. Two Los Angeles officers can be seen holding him down on a Hollywood street; one punches him several times in the face before they are able to handcuff him.

The Los Angeles Police Department is also investigating the officers' conduct.