Someone who works for a business but pretends not to in order to seem like a reliable source is a shill. Shill marketing is the act of using a shill to try and convince the public that a product is worth buying. Sometimes illegal, this practice is usually considered dishonest. If customers find out that they have been targeted with shill marketing, they often feel cheated.
The concept of shill marketing is simple. People tend to feel more comfortable with a product or service if they know someone else who has a good experience with it. If someone who isn't associated with the company tells you how good it is, the claim will probably be more convincing than if it came from the company spokesman.
A shill marketing worker is actually employed by the company, but pretends not to be. The marketer acts like a regular customer and tries to encourage people to buy the product. Oftentimes, multiple shills work together, reinforcing each other's story and engaging in a conversation about how great the product is.
The Internet has become an ideal venue for shill marketing. Since the Internet is anonymous, shilling is much easier. One person can pretend to be several different customers in the same shill marketing setup. Chat rooms, message boards, and blogs are common stages for an Internet shilling campaign.
Employees engaged in a shill marketing setup register one or more accounts on an Internet service, a message board for example. Usually one of the shill marketers will ask an innocent sounding question. "I was interested in buying product X. Has anyone heard anything about it?" This is the classic setup.
Another user, possibly the same person using a different account login, will answer the first question by praising the product. "Oh yeah, I started using product X a month ago and I love it. I use it all the time. It's the best product in the whole world!"
Shill marketers sometimes try to bring other members of the message board into the discussion, but the hook is already set. Anyone who isn't familiar with the shill setup might believe that the endorsement is real, and not just a cheap trick. Obviously, not all product endorsements are shill marketing in disguise. If the setup seems too perfect, and the answer is quick and only offers rave reviews, it's possible that you're not seeing an actual testimonial, but shilling in action.