This is usually sent to someone that is known to have a wireless email device and it is usually sent close to the last minute. Bailmail is most frequently sent from someone who has found something better to do.
Bailer's Buddy: Hey, don't you have to get to that dance thing in a few minutes?
Bailer: Nope. As soon as I found out there were free drinks here, I fired off a bailmail. I'm set for the night.