We just had a short outage on Beanstalk, which required a quick reboot on our slices at Engine Yard. While this situation really sucks, it happens. The best thing you can do is let people know you're working on it and update them on the progress. By using Campfire, we're able to give people an extra sense of comfort that real people are hard at work on the problem. In the end, a negative thing becomes a positive experience.
When we combine this with our Twitter account and site notices, we can properly inform our customers when things go wrong.