In the wake of Penny Arcade drawing attention to the issue through a comic and two front-page posts, concerns about "manchurian fans" shilling for companies in exchange for money or products have begun to draw wide attention in the electronic gaming community.
The case that's drawn most of the attention is that of Nvidia, though recent evidence suggests that what at one point appeared to be fans shilling in exchange for hardware was actually something less sinister. Quoth Joystiq:
Stephanie Schopp, an employee of Nvidia's marketing buddies at AEG, [assured] us that "the program... is far less nefarious than your rather damaging article/blog above claims it to be." She continues, "These members were not 'paid in hardware' as your article states, but sent hardware to give us (NVIDIA through AEG) feedback, positive or negative, regarding their experience with it. They were never told what to say, nor did they sign any document forbidding them to discuss their relationship with NVIDIA or AEG. They are not actors: they were real, informed, hardware enthusiasts that could help us further understand what it was the community wanted from hardware vendors." She then directs us to two posts regarding the issue.
Even if Nvidia's wasn't trying to persuade gamers to act as company plants, however, the case highlights the fact that other companies almost certainly are. The updates to a post at Boingboing suggest that the practice (known as either Astrotufing or Ashleeturfing) is far from uncommon. In addition to being grossly unethical, it's a strategy that's guaranteed to backfire when discovered. In fan communities which privilege accurate information (such as reality-show spoilers and and those dependent on accurate reviews), there's no one more hated than a liar or a shill.
Update: Penny Arcade's posted another comic on the topic. In addition to being funny, it suggests that this issue isn't going fade from public consciousness any time soon.