In the early days, search engines were the first stop when you got on the Internet. Later, free email clients like Hotmail, Yahoo!, Gmail, etc became the traffic magnets. Over time, as web technologies advanced further, there was a shift toward social networking sites, blogs, discussion forums, etc that allowed live interaction amongst users.
The impact of all this user generated content is that the online world has become a key source for getting bare truth about companies, people, etc directly from end users. You're planning to buy a property and want to do a quick check on the reputation of a particular builder, simply look it up on the Internet. You're facing issues with your mobile operator and want to know if there are others facing similar issues, then simply do a hash tag with your mobile operator and search for it on Twitter. You went on a holiday trip and felt that the hotel you stayed in offered lousy service, you can vent it all out on the various travel blogs out there. And likewise for any other product or service you purchased.
As a company, you can't really prevent users from saying negative things about you, but you can monitor what they're saying, and take preventive measures. This is a field known as online reputation management, and is becoming increasingly important for organizations. There are many tools and techniques that crawl the web and provide you all this information in a single place (we've reviewed one of them, TrustYou for the hospitality industry this time).
While such tools can help companies get and maybe even control the negative feedback, it's not a permanent solution or cure to your problems. If your company's product, customer service, or anything else is lousy and getting bad ratings, then the only cure is to improve it. Moreover, if you don't improve, your competitors could easily find out and leverage it to their own advantage.
Smaller organizations might feel that this area is not meant for them, and is only for larger enterprises. But actually, SMEs could learn from the mistakes of the bigger brands. In fact, smaller organizations are better poised to build a good reputation online because they're more agile, with lesser bag and baggage of bureaucracy, process approvals, etc.