Could this "out-of-office" note be synchronized from a central employee directory, e.g. Microsoft AD?

great idea!

This would be incredibly useful for highly active environments such as ours. A multi-faceted approach which adds a badge to user profiles & vcards, and also notifies a user when they @mention or share to an OOO user that the person is on leave, would be an excellent start. Perhaps this can tie in with Events in some way down the road, but a simple status option in the beginning is still great progress.