[Mivo]

In my field (social/video games), this kind of thing is fairly common. Often, the difference between rabid fanboys and actual sockpuppets is only marginal, though, and in the end negligible on the practical level: to get a somewhat objective and realistic take on a product that you're about to spend money on, a handful of feedback sources isn't enough, unless you know they're reliable or have shown to share your preferences.

The irony of it all, though, is that if employees introduce themselves as company representatives, not only can they say all the positive, hype-y stuff, but forum users appreciate their presence, and it would improve sales. Sockpuppets and fanboys, whether legitimate or not, rarely convince others of buying something, and if a product is poor, there will always be more (and more vocal) upset customers than sockpuppets.

But if you say, "Hey, I work for this company and I'm here to answer questions and talk about our stuff!", then people will not only listen, but may well buy the products, because customers love companies that interact with the community and with customers on an approachable, personal level. There's simply no need for socketpuppeting.