A search for @SFBART on Twitter Friday evening returned a long and growing stream of complaints against the Bay Area Rapid Transit system. But the outcry wasn't over delays or the usual transit gripes. Rather, people were chiming in at the behest of Anonymous and others to register outrage over the system blocking cell phone reception in its stations to quash protests on Thursday night.

BART had braced for large-scale disruptions on Thursday as activists planned to protest the deadly July 3 shooting of Charles Hill by BART police. Protests are a fairly routine thing in San Francisco, so while riders prepared for a bad commute, there wasn't huge news value to the planned demonstrations. But then the agency did a weird thing by deliberately interfering with cell phone reception as a way to disorient protesters. "BART asked wireless providers to temporarily interrupt service at select BART stations as one of many tactics to ensure the safety of everyone on the platform," spokesman James Allison said in a statement to CNET on Friday. A statement on BART's website on Friday afternoon had the following explanation:  

A civil disturbance during commute times at busy downtown San Francisco stations could lead to platform overcrowding and unsafe conditions for BART customers, employees and demonstrators. BART temporarily interrupted service at select BART stations as one of many tactics to ensure the safety of everyone on the platform.

The protests didn't really materialize on Thursday, perhaps because of the cell phone jamming, perhaps not. But because the agency used the controversial tactic, it has a whole new headache on its hands. Hactivist group Anonymous opened a chat room on Friday to brainstorm retaliatory moves, but so far just the Twitter protest has taken hold. Still, it's obvious that BART's tactic touched a nerve with technology and information activists. "I hope BART realizes that the whole WORLD is taking note of their actions. I'm watching Egyptians tweeting about BART's cell shutdown," tweeted Jillian C. York, the director of international freedom of expression at the Electronic Frontier Foundation. 

Observers soon turned to the question of whether the service shutdown was legal. At SFGate, blogger Zennie62 quoted extensively from the Communications Act of 1934 and the Federal Communications Commission website, coming to the conclusion: "Only Federal agencies can block cell phone use and with that, only under specific circumstances. BART is not a Federal agency." Gene Policinski, executive director of the First Amendment Center at Vanderbilt University elaborated. "Government can legitimately stop speech for public safety purposes, but it has to be the narrowest possible response, it has to be reasonable, and there has to be an imminent threat," he told the Christian Science Monitor. "It can't be done on mere speculation."

The significance of cell phones' role in protests has of course been highlighted lately in the London unrest, where rioters used Blackberry Messenger to stay ahead of police. On Friday, a teenager from Essex was charged with "Blackberry incitement" in allegedly helping perpetuate looting and rioting.