Just go read Gavin.
When you’re done, come back and read about Americans for Prosperity (listed on the Houston Tea Party site as "local sponsor") and its President, Tim Phillips:
Before replacing Koch Industries lobbyist Nancy Pfotenhauer as president of Americans for Prosperity, Timothy R. Phillips had a long career as a conservative operative. In 1992, Phillips managed Rep. Bob Goodlatte’s (R-VA) first Congressional campaign and served as his chief of staff for four years. In 1997, Phillips co-founded public relations firm Century Strategies with Ralph Reed. There, Phillips oversaw “direct mail, telemarketing, coalition building and strategic services” for the 2000 and 2004 Bush for President campaigns, and specialized in “grasstops” operations to establish fake grassroots organizations. [Century Strategies (Internet Archive)]
I guess that’s what Glenn Reynolds considers "pure grassroots."
Oh, gotta stop laughing. I’m hurting myself.