During the first phases of
the Microsoft trial, several
journalists and
advocates reported that
Microsoft had instructed some of its employees and partners to write
letters to the editor and
opinion articles in Microsoft's defense. Trouble was, the writers didn't exactly come out and
say they were
MSFT employees and
partners. The purpose of this operation was to create the
illusion of massive
grassroots support for Microsoft's position.
Some clever commentator decided that the appropriate word for "phony grassroots" is "astroturf". Thenceforth, any suspected shill for Microsoft or another large interest has come to be known, in some circles, as an "astroturfer". Astroturf is distinct from FUD in that astroturf's purpose is to create the illusion of public opinion whereas FUD attempts to cast doubt and uncertainty upon a competitor.
Update, August 2001: Recently, Kevin Reichard, the editor of Linux Today, admitted having trolled his site's own message boards. Under several pseudonyms such as "George Tirebiter" and "Rosh", Reichard posted anti-Linux (and particularly anti-GNU) flamebait, and attacked competing tech news sites. His actions have been widely reported as "astroturfing", and Slashdot linked to this node to clarify the term's meaning.
In the sense defined by Microsoft's earlier actions, Reichard was astroturfing when he posted attacks on competing sites. He masqueraded as a member of the general public and claimed to represent general opinion. However, in posting anti-GNU flamebait he was more simply shilling, or baiting the audience -- his intention was not actually to create the appearance of public opposition to GNU/Linux, but rather to create flamewars, thus drawing hits to Linux Today and thus increase ad revenues.
Reichard's actions were clearly contrary to journalistic ethics and basic honesty. They blurred the lines between news, editorial policy, opinion writing, and advertisement, and used deception as a means of increasing revenue. There is, however, no evidence that Reichard was paid by Microsoft or any other organization opposed to open source.