Barack Obama’s campaign held 5,000 local meetings across the country last weekend, and along with the nachos and celery sticks, supporters munched on a pep talk from the candidate himself, speaking online from a public library in Onawa, Iowa.

As The New York Times reported, however, some gatherings were poorly attended and their hosts “had a lonelier afternoon than they had hoped.” Only three visitors showed up at an apartment in Brooklyn and the Internet feed from Iowa kept breaking down.

Obama’s “community kickoffs” demonstrate the great strengths and weaknesses of the Internet as a political tool. Without a doubt, it has an enormous potential for raising money and mobilizing volunteers. The main target: hard-to-reach younger voters who are completely comfortable receiving information through the Web.

But it’s not easy prying those same people away from their computers and training them to meet strangers, organize events, knock on doors and drag voters to the polls. No one has fully solved the problem that torpedoed Howard Dean, who built a large and lively community of Web-based supporters in 2004 but flamed out in the Iowa caucuses.

Obama’s campaign manager, David Plouffe, told The Washington Post that he was studying Dean’s failure in Iowa and trying to learn from his mistakes. The most obvious one: of Dean’s 650,000 Internet supporters, only about 2,500 lived in Iowa, which meant that most of his ground-level organizing had to be done by out-of-staters.