My answer doesn't quite fit the poll choices. I never take a spare when touring on my 700c touring bike. Figure I can always make do somehow to get to the next place that sells tires. But I do carry a spare when using my Bike Friday with 451-size tires. Those are pretty hard to find so I'd probably have to have them overnighted out from somewhere and it would be a serious inconvenience. They're also much smaller tires - I don't bother with the folding bead type since folding a wire bead into three loops lets me put the spare tire into one of the small outside pockets of my panniers.