GM sends the surveys to customers' homes to reduce the chance of tampering, but some dealers have been known to offer customers incentives if they are allowed to fill out the surveys themselves. Customers can find it hard to pass up a free tank of gas in exchange for a 27-question survey they may not care about.
While customers should be upset that their dealer opinions might not be recognized by the company, but dealers accused of this have a lot more to lose. Automotive News says dealers are awarded bonuses according to their customer satisfaction scores and can make as much as $420,000 each quarter depending on the dealership's sales volume. With that kind of money, some GM outlets may find it hard to resist cheating.
[Source: Automotive News - Sub. Req.]