Quoth Wiki: Astroturfing is a word in English describing formal political, advertising, or public relations campaigns seeking to create the impression of being spontaneous "grassroots" behavior, hence the reference to the artificial grass, AstroTurf.
There's a nuance to Astroturf that doesn't register with me. Consider this example: "Between the 1960s and today, however, the mediaspace through which these causes disseminated ideas and gained momentum has changed. The best techniques for galvanizing a movement have long been co-opted and surpassed by public relations and advertising firms. Whether a movement is real or Astroturf has become almost impossible for even discerning viewers to figure out." - Douglas Rushkoff, An End to Movements, arthurmag.com, 15 Aug 2009.
Then, in a comment response by a reader: "These are just more reasons that corporate speech should always be regulated as commercial speech, whether it is in the form of campaign contributions, astroturf, or any other form of political spending on behalf of a for-profit entity." - James Salsman.
And another, worked-up enough to try some verbing: "The portrayal of the protests as the voice of the youth speaking out against an unjust war that they were being drafted into was effectively anti-war astroturfing in the same way that these 'ordinary Americans' anti-health care reform protesters. So here’s a question: what if they aren’t astroturfing? Does it matter? Not to me."
I don't quite get it. Up until 10 minutes ago I'd only heard this word in connection with artificial grass for sports fields.