<<I use my bar-end mirror and move over to within 8" of the shoulder but some fool feels the need to yell "on your left" at full song. >>

I would much prefer them to shout "on your left" than nothing at all, even if I've seen them coming. It's a bit like getting into the habit of using using your turn flashers when driving even if nothing else is around. That will never happen in FL, of course as most don't know what that little stick to the left of the steering wheel is for