, the favorite web business of political sociologists, announced yesterday that it will institute a fee for its community organizing service beginning May 1.

The fee is nominal: $19 per group per month. Since groups don’t meet unless they have five people who agree to attend, a Meetup willing to split the tab equally will exact less than $4 from each person. Alternately, one member can treat the others; it’s up to each group to decide.

Meetups have glowed with the promise of being an alternate source of grassroots political energy ever since the palmy days of the Howard Dean campaign in early 2003. More than 1.7 million people have met up in 50 countries with others who share their interests in topics political and non-political – although in this recent Fortune interview, Meetup CEO Scott Heiferman says that even groups organized around dogs and knitting have a tendency to veer into civic life.

Will the fee cast a shadow on the grassroots? In the fall of 2001, our survey found that one in six internet users (17%, or 19 million people) had been asked to pay for content or web site access that used to be free. Half of them found a free alternative, 36% completely stopped getting the content or access, and 12% paid.

That was then. We will update the finding soon.