Today American taxpayers in more than 300 locations in all 50 states will hold rallies -- dubbed "tea parties" -- to protest higher taxes and out-of-control government spending. There is no political party behind these rallies, no grand right-wing conspiracy, not even a 501(c) group like MoveOn.org.

So who's behind the Tax Day tea parties? Ordinary folks who are using the power of the Internet to organize. For a number of years, techno-geeks have been organizing "flash crowds" -- groups of people, coordinated by text or cellphone, who converge on a particular location and then do something silly, like the pillow fights that popped up in 50 cities earlier this month. This is part of a general phenomenon dubbed "Smart Mobs" by Howard Rheingold, author of a book by the same title, in which modern communications and social-networking technologies allow quick coordination among large numbers of people who don't know each other.

In the old days, organizing large groups of people required, well, an organization: a political party, a labor union, a church or some other sort of structure. Now people can coordinate themselves.

We saw a bit of this in the 2004 and 2008 presidential campaigns, with things like Howard Dean's use of Meetup, and Barack Obama's use of Facebook. But this was still social-networking in support of an existing organization or campaign. The tea-party protest movement is organizing itself, on its own behalf. Some existing organizations, like Newt Gingrich's American Solutions and FreedomWorks, have gotten involved. But they're involved as followers and facilitators, not leaders. The leaders are appearing on their own, and reaching out to others through blogs, Facebook, chat boards and alternative media.

The protests began with bloggers in Seattle, Wash., who organized a demonstration on Feb. 16. As word of this spread, rallies in Denver and Mesa, Ariz., were quickly organized for the next day. Then came CNBC talker Rick Santelli's Feb. 19 "rant heard round the world" in which he called for a "Chicago tea party" on July Fourth. The tea-party moniker stuck, but angry taxpayers weren't willing to wait until July. Soon, tea-party protests were appearing in one city after another, drawing at first hundreds, and then thousands, to marches in cities from Orlando to Kansas City to Cincinnati.