Incidents of cellphone theft have been rising for several years and are fast becoming an epidemic. IDG News Service collected data on serious crimes in San Francisco from November to April and recorded 579 thefts of cellphones or tablets, accounting for 41 percent of all serious crime. In just over half the incidents, victims were punched, kicked or otherwise physically intimidated for their phones, and in a quarter of robberies, users were threatened with guns or knives. This isn't just happening in tech-loving San Francisco, either. The picture is similar across the United States. A big reason for such thefts, until recently, is that there had been little to stop someone using a stolen cellphone. Reacting to pressure from law enforcement and regulators, the U.S.'s largest cellphone carriers agreed early last year to establish a database of stolen cellphones."