Going off on a tangent...
For all of the cries about "crow hops" and "leaps", the most common pitching violation I probably see is the pitcher stepping onto the plate with her hands together.
I do call it when I see it and, inevitably, when I do I get the old, "She's never been called for that before". It's an old excuse, but now I'm starting to believe it.
Two weekends ago I went to a clinic for our local high school umpire group. One of the exercises had all of the umpires- there were about 70 there- standing around while someone simulated various legal and illegal pitching moves. If we saw something illegal, we were asked to signal and call it just as we would during a game.
Everyone was calling the obvious stuff (licking fingers and touching the ball, feet not correctly on the pitcher's plate, double touches, etc.). Then, the pitcher stood behind the plate, brought his hands together, and stepped onto the plate.
Of the 70 umpires there, I was the only one who called out "illegal"!
Maybe all these pitchers really haven't been called for this before...