The White House convened the first “Twitter Town Hall” in American history on Wednesday, as President Obama answered a battery of short questions posted on Twitter, the buzzy social network, which were culled from thousands of submissions by Americans around the country.

The event combined a novel experiment in social media with some traditional political tactics. So while the White House did not have a sense of specific questions in advance, it sought to control the message by limiting the topic to the economy, and by hand-picking a moderator, Twitter CEO Jack Dorsey, who was unlikely to be intensely journalistic or adversarial. (Obama had the same luxury in his recent event at Facebook, where he was rarely pressed or interrupted by founder Mark Zuckerberg.)

Throughout the event, Dorsey read questions off Twitter, but did not prod or press Obama. This allowed the president to stay on message—he rarely departed from his well-worn talking points on the flagging economy, debt ceiling negotiations, and renewable resources.

Still, Twitter enabled an impressive scale for public participation in the town hall.

Over 40,000 questions were posted on Twitter, and some of the most popular—by virtue of retweets—made it into the event, including queries about the Bush tax cuts and strengthening NASA’s space program. Other grassroots favorites, like whether pot should be legalized to increase revenue, failed to get a nod from Dorsey.  A third of all questions were from people on the East Coast, where the event ocurred in the afternoon, while 16 percent of questions came from the Pacific timezone, and only 5 percent from people tweeting in Mountain time.

By PR standards, Wednesday was an easy win for the White House. An analog version of a similar conversation, with Obama pressing his economic agenda, would not draw this kind of coverage. And driving more people to Obama’s Twitter accounts, which already have an impressive 11 million followers, is useful as Obama’s re-election campaign gears up.  But overall, this was still a pretty low bar for online civic participation.

The administration’s forays into civics online, as I’ve argued before, have not met the public demand for deeper interaction with elected officials. Nor have they provided the kind of transparency and independent, citizen advocates who can use these forums to raise concerns of the public that are not presented, for whatever reason, by the current media and political establishment. That is probably the most significant promise of this kind of citizen media—as past questions about torture and drug policy have demonstrated—and it’s not the kind of change that the White House is going to force on itself.