Er...probably not the real subject of this thread...but...if you play by ear and 'feel' the blues, and then learn a few more techniques from books etc (rather than just by listening to others, then trying it yourself,) it doesn't seem any less valuable to me. I sometimes play with a classically trained cellist (blues and folk music) and have learnt loads from her AND I would like to think she has learnt a little from the way I approach music, more by going with what feels right and busking from the heart. Playing music is amazing and if you stop trying to experiment with it and get stuck doing the same old things, it is a shame cos you can always learn more. Like a guitarist who only plays 3 chords then suddenly learns another one...
It takes all sorts thank goodness, we all approach music in different ways and I will now go back and see if I can understand any of the technical talk above and nick some ideas!