Punto - I am just playing devil's advocate. In order to deflect the air to follow the curved path along the wing an acceleration downwards (relative to the wing) is required - if the air is in contact with the wing, it must push down on it (as the wing will push up against it)
However, jymil's post with the turning of fluids is a graphic which does show downward displacement - the cambridge video is actual streamlines which show negligible downwards displacement but a significant upwards displacement.
Which of these is the bad science?
If all the clever scientists in the world can't agree, what hope have us mere pilots got?
It would be nice to have a definitive explanation - probably a combination of all the current theories.