The internet is a vast and largely unregulated space, not too dis-similar to the gun slinging days of the wild wild west. It does make the challenge of online reputation management a tricky one. How do you protect your reputation when your clients, or even strangers, can say anything about you, on any site and potentially tarnish your brand?
SEO Book has a good selection of tips to manage your online reputation. The article talks about the importance of being proactive, and using many tools that can aid you with reputation management – many of them free, such as Google Alerts.