It seems the Federal Trade Commission also don't like astroturfing:
A public relations agency hired by video game developers will settle Federal Trade Commission charges that it engaged in deceptive advertising by having employees pose as ordinary consumers posting game reviews at an online store, and not disclosing that the reviews came from paid employees working on behalf of the developers.
“Companies, including public relations firms involved in online marketing need to abide by long-held principles of truth in advertising,” said Mary Engle, Director of the FTC’s Division of Advertising Practices. “Advertisers should not pass themselves off as ordinary consumers touting a product, and endorsers should make it clear when they have financial connections to sellers.”