Officials at Bay Area Rapid Transit (BART) decided Monday that cutting cellphone service to thwart another planned protest would cause more trouble than the protests themselves. Instead, four stations were temporarily closed, creating a chaotic rush-hour commute.

About 50 activists protesting two BART police shootings managed to disrupt local train service Monday evening as transit officials closed several central stations to commuter travel. Before the protests began, protesters held cellphones to their ears and loudly said, "Can you hear me now?" Unlike last Thursday evening, this time they could.

Despite the presence of officers dressed in riot gear, no arrests were made.

The decision by BART to briefly cut cellphone service at four stations last Thursday drew widespread criticism by free speech advocates, a promised lawsuit by the ACLU, and a hack of a BART website by the online activist collective Anonymous, which posted personal information of thousands of BART website users on a separate website this weekend in retaliation.

After meeting with BART officials Monday, the ACLU said it won't file a lawsuit over last week's service disruption. The transit agency took that step out of concern that the planned protest would become violent, as did an earlier protest, on July 11, held to condemn the shooting of a homeless man by BART police. The civil liberties group said, however, it is disappointed that BART left the door open to future cell service disruptions. The Federal Communications Commission has opened an investigation into whether BART broke federal law by turning off four agency-owned cellphone transponders last Thursday.

Officials said they "debated to death" the issue of whether to cut cell service Monday night. Spokesman Linton Johnson maintained Monday that cutting service was again an option to protect rider safety. But as the time of the protests drew closer, the transit agency decided against it, mainly because of the public backlash.

“It’s dangerous for activists to amass in a train boarding platform,” BART board member Tom Radulovich told the San Francisco Examiner. “But to shut down cellphone service was a bit of an overreaction, and it has energized a whole new group of people to target BART.”

The debate at BART dovetails into a global debate about the role of social media in fomenting social unrest in places like Tehran, Cairo, and London. The US, too, is witnessing a growing number of "flash mobs" organized via social media, all of which criminologist Sean Varano at Roger Williams University says is starting to "break down our conventional understandings of crime."

But government agencies' efforts to attack what they see as criminal use of social media can run afoul of the Constitution's guarantee of free speech, especially if sanctions, like BART's decision to cut cell service, are too broadly applied, says Gene Policinski, director of the First Amendment Center at Vanderbilt University, in Nashville.

The BART incident shows that "we're right at the threshold of a number of questions raised by social media," says Mr. Policinski.

BART shut down cell service Thursday to thwart the efforts of demonstrators protesting the police shooting death of Charles Blair Hill on July 3. Discontent with BART police has been festering since the shooting death of Oscar Grant in early 2009. Officers involved with that shooting received what many saw as lenient sentences.

The BART decision to close several stations Monday caused minor chaos, as many commuters, including tourists, were forced to find other ways to their homes and destinations. Some commuters, the Examiner reported, "walked from station to station, chasing rumors – many originating from BART officials themselves – that they had reopened."