It was like something out of a movie: a US Capitol Police Special Agent and three San Francisco cops drop by a suspect's home to ask about threatening phone calls targeting House Speaker Nancy Pelosi. They know the calls all came from a specific phone number, one assigned to the VoIP provider magicJack, but the suspect denies that the number is his. The agent steps into the other room and uses his cell phone to call the number. A telephone connected to the suspect's computer starts to ring, and the suspect answers it. "Hello," says the agent.
http://arstechnica.com/tech-policy/news/2010/04/harrassing-nancy-pelosi-yes-feds-can-trace-magicjack-calls.ars