Do a lot of kayakers have one. I have seen a lot of them in yaks that are not very visible in some very sketchy spots, like away from the bank on blind corners or paddling down the middle of the lake. I have nearly run over one guy at Stockton who has a custom, beautiful, wood yak that is nearly perfectly camouflaged with the background of wood and rocks that is prevalent down there.
Once in a while I see someone in a brightly colored one or wearing bright clothing. Even a few of them have flags that are highly visible. I’m really surprised that we don’t have more boat/yak collisions on our lakes.