I've never given it much thought but while jamming, I noticed that most of my friends had their thumbs considerably over their neck, while mine generally never is, unless I'm doing thumbed-chords. The only other exception I use thumb-over-neck is while bending the higher strings. When it comes to playing 3nps string patterns or whathaveyou, my thumb is generally slanted and bent is a 90 degree angle.
Now. Is having a hitchhikers thumb a virtue or a curse? Granted, I've NEVER had any problems in terms of my thumb being a liability, but I generally find that some stretches I do, I could never be able to do without my thumb. I noticed that Shawn Lane had a hitchhikers thumb as well, where as players like Paul Gilbert clearly have their thumbs over-the-neck while playing fast stuff.
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