Just a short rant.
Any rational paddler knows that not wearing a PFD is foolish, but did you know that it is also selfish and inconsiderate ?
Not wearing a PFD puts other members of a paddling group at higher risk during rescue for several reasons. Paddlers who suddenly become swimmers often panic. A panicked swimmer is one of the most dangerous things in the water. They may desperately grasp onto anything to save themselves, including a rescuer's boat, their paddle and even the rescuer. If the swimmer capsizes the rescuer they may push down on the rescuer to push themselves up. The swimmer is also not able to hold onto their gear while they are swimming adding these items to the list of things needing rescue. If their hands and legs are occupied with swimming, they can not assist in their own rescue. Unconscious swimmers not wearing PFDs sink, often leading to breathing of water (that's not a good thing). It is very difficult to rescue someone who has sunk. If you capsize in water that is 60 degrees or below you will probably experience "cold water shock". When this happens you hyperventilate uncontrollably for 3-5 minutes and lose motor control. If you cannot control your muscles, you cannot swim. If you uncontrollably inhale as water hits you in the face, you will inhale water, not good.
So, if you don't wear a PFD, don't paddle with other people. If you do wear one, don't paddle with people who don't. If you organize or lead trips, don't allow people to go bare back on your trips.