For years I played with my thumb anchored to the back of the neck, lifting and moving as needed, as did everybody else I saw. Recently I read a section in a book by a bassist (may have been Gary Willis) that keeping your thumb off the neck relieves pressure and allows quicker position changes and a greater reach. I have found all this to be true, and the top fret access on my bass just got a lot easier. But are there any reprecussions to this? Anything of which I should be wary?