Yesterday, the hacktivist group Anonymous got itself involved in a San Francisco protest against BART (Bay Area Rapid Transit), the city's subway system. Four BART stations were shut temporarily during a demonstration organized by the hacker group in response to two grievances: the July shooting of a man by police, and the transit organization's subsequent blocking of cell phone calls to try and prevent demonstrations by protestors.

Last week, BART reportedly cut off power to its wireless nodes after learning that demonstrators planned to use social media and text messaging to organize a protest against the shooting, a move that has troubled civil libertarians.

The shutdown of the wireless towers helped raise questions about the role that social networks are playing in helping people, from Egypt to London, organize online. In the U.S., with its history of free speech, critics are saying BART's move was unconstitutional, TIME magazine is reporting.

BART's shut-down of the towers has prompted an FCC investigation into the legality of the transit company's actions.

On Sunday, Anonymous organized an attack on one of BART's Web sites, posting the personal information of more than 2,000 passengers online, as well as calling for yesterday's protests.

“We are Anonymous, we are your citizens, we are the people, we do not tolerate oppression from any government agency,” stated Anonymous. “BART has proved multiple times that they have no problem exploiting and abusing the people.”

A few dozen protesters showed up at the stations during rush hour. The protest ended when BART authorities closed the Civic Center station, and then three others.

Police said there had been no arrests, although officers arrived dressed in riot gear, the UK paper The Guardian is reporting.

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