In the wake of a Blizzard Warning, issued Monday afternoon set to start at midnight, Southwest and other airlines canceled flights departing last night and this morning. I received an automated cancellation call at about 4:30pm informing me that my own 6:40am flight was canceled. I rescheduled and went to bed. Woke up this morning to find that the blizzard never happened. Since I ended up with an extra half-day off of work, the cancellation really doesn't bother me but I have to imagine a situation like this may suck for the airline.
Anyways, I was wondering....

Do they end up flying the equipment with no passengers for the multi-stop flights? Do they ever un-cancel flights in a situation like this?

Also-
Interestingly, southwest.com still allowed me to book tickets on these canceled flights.