I often encourage people to give their honest feedback. I find that to be one of the quickest, least expensive ways to imrove ones company. Find out whats wrong from the horses mouth.
Example. You own a restaurant. You just hired the most wonderful waiter but your repeat customers aren't repeating anymore. Instead of spending hundreds of dollars on a new marketing campaign... why not ask the customers you currently have if they think anything could be improved? If you ask your wait staff, they will more than likely tell you what you 'want' to hear vs. 'need' to hear, because thats what you pay them for.
If I personally ate at your restaurant, I may have gone home and done one of two things. Signed onto Facebook and 1) told everyone what a wonderful experience it was and why or 2) told everyone that I thought the owner might be asleep at the wheel on this one. <-- Folks. Face it, there are a lot of people like myself out there. Thus the creation of Yelp.com. Genius. Monitor your social identity using facebook. If you find something to be insulting... thats ok. Be humiliated. Then change it. We all make mistakes, its part of evolution.
My point is, you can't blame the consumer for voicing thier opinions on facebook. Because they were doing it before facebook via email or phone call. People aren't going to censor themselves for your benefit. Take pride in what you do, realize they are the reason you are able to own a business and give the people what they want.
Never for a second think someone isn't talking about you and keep in mind, facebook isn't the devil.