I had an opportunity to watch some really spectacular foot faulting the other day. The opponent server lined up right on the middle hash and would step over the middle to serve every time to the deuce court.
It wasn't even close he would cross the middle going into the same side that he was serving to all prior to throwing up the ball for the toss.
I probably should have said something, but since they were already hooking us on line calls I figured it would be a big fight for no benefit. (We had been breaking his serve every time)