h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

and, not surprisingly, the slightly uneven surface of the rotating ball slughtly distorsts the airflow about the spheroid, so there can be an element of control involved, depending on the 'pressure point' (high, low, middle)applied to the ball.
even a fairly even texture and resiliency of the ball and the medium involved can come into effect, as in backspin or sidespin on a billiards table (felt-covered slate) or tennis court (clay or grass....or concrete.)
on baseball, the pitcher can alter the 'pressure point' with some reasonable degree of consistency. thus, a thrown baseball with the fingers along the seams acts differently when thrown with the same grop and pressure when thrown 'against' the raised seams.