Bad news for the casual carpooling program
According to an article in SFGATE: Woman escapes carpool carjacker / Man said he had a bomb, then hit her and stole her car.
The title basically summarizes the article. Casual carpooling has been quite successful for several decades enabling people to use the HOV lane by getting non-drivers to ride as passengers, with very few if any reported violent acts.
It is used in Washington along the Shirley Highway, as well as San Francisco, where it is called Slugging.