SAN FRANCISCO — Despite a 72-hour Twitter and e-mail campaign by members of the online hacker collective Anonymous, a demonstration at a San Francisco subway station drew what appeared to be less than a few dozen protesters Monday.

Instead, the Civic Center station platform here was riddled mostly with riot-gear-dressed police officers and camera-wielding members of the media. This time, officials resisted the temptation to switch off cellphone service.

Anonymous had called the demonstration to protest the subway system’s dubious distinction as the first known government agency in the United States to shutter mobile-phone and internet service to quell protests. The Bay Area Rapid Transit system unplugged service for a few hours Thursday in anticipation of a protest — that never materialized — against BART officers’ killing of a homeless man the month before.

The hackers of Anonymous initially responded over the weekend by defacing the agency’s website, and stealing and releasing the private account information of some 2,000 San Francisco–area transit riders. Then it used Twitter and the web to call for a real-life mobilization that captivated the virtual world, but fizzled in real life.

“No justice, no peace. Disband the BART police,” roughly a dozen of the protesters chanted in unison, referring to July 3 shooting death of a knife-wielding homeless man by BART police.

Only a few protesters were seen wearing a Guy Fawkes mask, the symbol of Anonymous. ”I believe in free speech,” said one.

The authorities did not immediately report any arrests.

Briefly, however, the climate got heavy when a bearded man flailed and bobbed around armed officers while chanting, “Can you hear me now?” Only a handful of trains stopped in the station, as many continued through.

The American Civil Liberties Union met with BART officials earlier in the day about the Thursday cell phone shutdown, and decided not to file legal action immediately.

Photos: Jon Snyder/Wired.com