That's what this article in the New York Times explores, along with how some hotels try to game the system to make their properties look better. There is a problem with all the online ratings systems, for Amazon to TripAdvisor, I think, in that most people are more likely to post something when they've had a bad experience than a good one. Just human nature to do that. But I also think hotels are wrong to try to bribe people into writing glowing reviews by giving away spa treatments or room rate discounts. These folks, quoted from the article, have the right attitude:
The Hilton Hotels Corporation, which owns the Doubletree, Embassy Suites and Hampton Inn brands, also follows the ratings sites. But trying to influence the system by prompting employees or guests to write a positive review "would not be ethical," said Bala Subramanian, Hilton's senior vice president for distribution and brand integration.
"What's more, it's a waste of time," he said. "If we have a problem with one of our hotels, we want to address the problem, not rig the system."