This article from hotel-online shows just how anxious hoteliers are about having complaints go online freely, without their being able to do anything about what is said about them. The author preferred the days when it was just between a disgruntled guest and the manager to hash things out, because, he says, hotels now have no recourse.
To which I say, of course they do. Smart hoteliers should be monitoring the Internet (and blogs!) for mentions of their hotel, contacting individuals who have a beef, leaving comments telling their side of the story, etc., etc. I have so much respect for those who are willing to face the wrath of the public, and explain or apologize or defend themselves in a public forum. People are going to talk, no matter what they do. It's just that now, the conversation has spread from friends and family to the world. This isn't something to be afraid of—it's a tremendous opportunity to join in those conversations.
(My personal favorite of these sites is Hotel Chatter, which is careful to disclaim that the reviews are just one guest's view, and others may have a totally different experience.)
Update: Here's a great post about what to do about negative comments from The Diva Marketing Blog (thanks to Kevin for the pointer).