Do your best to resolve the issue with the dissatisfied person—publicly. It shows that you are persistent and take your customers' satisfaction seriously.
Take action to push the negative reports down in search-results pages. Submit a press release to PR distribution sites, or start a new blog about your company's products or services. Make sure you share the good information about your business, such as favorable stats or testimonials. All that good news will likely be listed in search results before the bad stuff.
Use social networking to build—and spread—positive buzz. People will refer your site if it has appeal for their peers. So provide pertinent and buzz-worthy info.
So in short: Hold your head up high. With proper planning and a few positive strategies, you can mitigate any damage done to your rep by a few bad comments—and you may boost your goodwill in the process.