In relation to the 700/26 swap potential. I don't think anyone was suggesting not carrying a spare tire or the potential to swap between 26 and 700 on the fly was an alternative to carrying a spare tire. It is not an either/or. It is knowing that if XXX happens, you can potentially do YYY. Maybe you limp into town with a broken 700c hub, if the only thing around is a used 26 MTB wheel/tire, it just might work as a temp solution. The more you know, the better off you are and knowledge doesn't add weight to your rig.