When people make changes to their Unshelved email delivery we ask them to leave a note. These are usually friendly, sometimes terse, and occasionally downright rude (people get really upset when you fail to amuse them). But my favorite recent explanation of why someone was taking themselves off the list was the following:

Leaving because going to Yukon for summer. No hydro where I'm going. Will run generator now and then but have to cut down email drasticly for the summer. See you in the Fall.