Social media has played a vital role in the Occupy Wall Street movement since it began as a Twitter experiment in July, when the anticonsumerism magazine Adbusters posted a suggestion for a Sept. 17 march in Lower Manhattan. And over the last two months, protesters used cellphones and social sites like Twitter, Facebook and YouTube to spread their message around the world.

Now, with cities starting to break up dozens of encampments from New York to Oakland, Calif., protesters may no longer have a physical presence that helps produce daily images and live streaming video for the 24-hour news cycle. And, despite having created a large network on social media sites, organizers within the movement and social media experts say that online tools alone are not enough to sustain it.

“I think the online component was critical — the ability to stream video, to capture the images and create records and narratives of sacrifice and resistance,” said Yochai Benkler, a professor at Harvard Law School and co-director of the Berkman Center for Internet and Society at Harvard. But he added that a complete retreat to an online-only form would be a mistake.

“The ability to focus on a national agenda will depend on actual, on-the-ground, face-to-face actions, laying your body down for your principles — with the ability to capture the images and project them to the world,” Mr. Benkler said, pointing to the outrage over the use of pepper spray at the University of California, Davis, last weekend as an example of an encounter that ratcheted up the online conversation.