Customer service that increases ROI
Facebook and Twitter make companies instantly accessible to customers. They should, anyway. It's expected that if an email is sent to customer support, there might not be an immediate response. But if it's tweeted or posted to a brand Facebook page, a quick response is sought. Addressing a question or issue swiftly not only gratifies the customer, but it is also an opportunity to publicly handle a customer service issue. If it is a question, time is saved for other customers with the same question. Anyone else thinking ROI here?

An added benefit to public customer service is that it could save telephone representatives hours and company dollars by addressing thousands of customers at once. Another way to do this is to poll customers about any number of issues. This provides an immediate response that can guide your approach, rather than waiting months or more for something to play out, such as interest in a new product or service.
Ideally there are never problems. But in reality, things happen, and some people are downright hard to please. It might seem risky to open a public platform for people to jump on and say anything, knowing it isn't always praise, but if the matter is at all inflammatory, there is an excellent opportunity to show the public how gracefully and diplomatically you resolve an issue. That's free, quality PR right there, and ROI increases again!