ASTROTURFING n. The use of paid shills to create the impression of a popular movement, through means like letters to newspapers from 'concerned citizens', paid opinion pieces, and the formation of grass-roots lobbying groups that are actually funded by a PR group (astroturf is fake grass; hence the term). This term became common among hackers after it came to light in early 1998 that Microsoft had attempted to use such tactics to forestall the U.S. Department of Justice's antitrust action against the company. (The Jargon Dictionary).
The most recent incident of astroturfing I'm aware of was perpetrated by Bush backers who had servicemen and women in Iraq "write" dictated form letters to hometown newspapers describing what wonderful things they were doing and how much the Iraqi people loved having them.
Then of course there are the infamous CNN Website "Question of the Day" polls conducted by Wolf Blitzer et al. which give readers an opportunity to weigh in oAtrion some topical issue. These polls are often posted by partisan bloggers--it's become almost a sport. Atrios is notorious for this. Just today he has a discussion about this poll.