I inadvertently corrupted a couple of mailbox stores (like anyone actually causes corruption intentionally) because of a lack of understanding. I hope this story will save someone else some pain.
The story started when an Exchange server's CPU was running at 100% for a long time, causing my monitor to alert us. After some intial troubleshooting, it was decided to restart the Exchange services. The restart process failed, the CPU continued to run at 100%.
We waited an hour, and the status had not changed. Figuring a reboot would resolve any ailments, we did just that. The server took a long time, but finally rebooted after 15 minutes. When the server restarted, some of the mailbox stores did not mount. After spending some time to try to fix things, we put in a call to Microsoft PSS.
The bad news
We discovered that our actions corrupted several mailbox stores (this was on an Enterprise Edition server). In talking to Microsoft, we discovered that a shutdown or restart of the Operating System does not necessarily wait for all services to stop. The Information Store service apparently did not stop completely and after a timed delay, Windows shut itself down. We were told that the corruption happened because the store was actively being written to when the service stopped.
With a new understanding of the Information Store service, whenever maintenance is performed on our Exchange servers, we always dismount all of the mailbox stores first. This assures that all "in flight" transactions are complete before the service is stopped.