Posts on blogs here and here use the term, and they define what they mean by it. “Astroturf” in this usage is a reference to grassroots efforts that aren’t. These campaigns look like an uprising by everyday people on some issue but are actually carefully orchestrated by consultants and interest groups who try to hide their roles. Consider the torch-wielding “Frankenstein” villagers on the march, only they’re secretly organized and paid by a foundation or think tank with some interest in the result.
It’s not a new practice, and the word has been used this way for a while, if this Wikipedia entry is to be trusted. The entry itself admits that Wikipedia is vulnerable to Astroturfing.
Thanks to these bloggers, I’ll be watching out for Astroturf — the word and the practice — from now on.