Why aren’t democratic dissidents as well-known in the free world today as the dissidents who challenged the Soviet empire were in the 1970s and 1980s?

Activists confronting repressive regimes in the 21st century often have all the communication tools of the digital age at their disposal — Facebook, YouTube, cellphones, e-mail. Yet none of them has achieved anything like the renown of Andrei Sakharov, Vaclav Havel, Alexander Solzhenitsyn, or the other indomitable souls who challenged communist tyranny in the decades before the Internet existed.

That paradox was posed last week by David Keyes, the director of CyberDissidents.org — an organization dedicated, in the words of its website, “to bringing the world’s attention to online democracy advocates and their plight.” Speaking at a conference on the Internet and contemporary dissent organized by the Bush Institute in Dallas, Keyes framed his agenda candidly: He wants to make the Middle East’s pro-democracy Internet activists famous and beloved in the West. Keyes was an aide to Natan Sharansky, the celebrated Soviet-dissident-turned-Israeli-statesman, and it was Sharansky who taught him that when it comes to antitotalitarian dissidents, “the more famous you are, the more protected you are.”

The best example of that phenomenon is Sharansky himself. The Ukrainian-born mathematician was falsely convicted of treason and spent nine years in the Soviet gulag before finally being released by Mikhail Gorbachev in 1986. Years later, Gorbachev recalled visiting Canada as a Politburo member in 1983, and being repeatedly peppered with questions about Sharansky, whom at that point he had never heard of. To Gorbachev personally, the refusenik’s fate was a matter of indifference. But Sharansky’s high profile in the West convinced the future Soviet ruler that Moscow gained nothing by keeping him imprisoned.

But how does a dissident behind an Iron Curtain attain that fame? At CyberDissidents.org, Keyes spotlights many of the Middle East’s pro-democracy bloggers with links to their writings, descriptions of their work, and photographs. But compared with the 20th century’s great Soviet and Eastern European dissidents, they might as well be anonymous.

“The Internet enables them to reach the world,” Keyes says. “They push the ‘send’ button and thousands of people can instantly read their words. Yet not a single American in a million knows their names.” Dissidents like Solzhenitsyn and Havel, by contrast, communicated through samizdat — laboriously produced underground writings, printed in secret and circulated from hand to hand — and managed to reach an international audience.

Perhaps the explanation for that puzzle lies in the very immediacy of the Internet itself.

Samizdat literature was difficult to create and dangerous to distribute; precisely for that reason, it was inestimably precious, far more likely to be read with care. But online writing is ubiquitous. There are nearly 2 billion Internet users, 350 million Facebook pages, scores of millions of blogs. Twitter publishes 600 tweets per second. No wonder cyber-dissidents struggle to be heard. Amid such a din of white noise, how are their messages supposed to draw attention?

And even when their blog posts and Facebook comments are noticed, how many are as substantial as the essays and manifestos the Soviet-era dissidents took such risks to write and read? “The new media is much more conducive to instant opinion rather than considered opinion,” says Radio Free Europe/Radio Liberty president Jeffrey Gedmin, who delivered a speech at the Dallas conference. With the rise of the Internet has come an amazing array of tools for communication. But dissidents need something wise and important to say.

Twitter is a great vehicle for letting people know where the rally will be held on Thursday, but it can’t tell dissidents how to replace a corrupt dictatorship with stable democratic institutions. When those “chain-smoking intellectuals” got together in their cramped apartments in Moscow or Prague, Gedmin says, it was to do some serious thinking about why communist rule was wrong, how it could be overthrown, and how it could be replaced with something decent and durable. “That was intellectual and conceptual heavy lifting — not Internet chatter or quick blogging.”

Democratic revolutions require such deliberation and philosophical nourishment — more than can be delivered in 140-character bites. The Internet is a medium like none the world has ever known. But the medium isn’t the message. And in the struggle for liberty, the message matters most.