John,
Thanks for the promo. I'm going to try to keep that section growing and I hope it can be the most useful part of the blog over time.
Doug,
Rule 0.5 in the Rules of Golf is don't believe everything that a commentator on TV says about the rules. It isn't if it hits the ball, only if it moves it.
The Rules of Golf draw black and white lines on a lot of things. One of them is that if you cause your ball to move, with the exception of some very specific cases, you are penalized. In the case of marking your ball, if your hand is right next to the ball and you bump it, there is no penalty, but if you drop something from any height, be it a ball marker, putter, hat or anything else and cause the ball to move you are penalized.
Rule 20-1 and 20-3 cover lifting and replacing a ball. They both state that there is no penalty for accidentally moving your ball in the act as long as the movement is directly attributable to the process. Dropping your coin or ball is not the proper way to do this and so it is considered to not be directly attributable.
The rules are not designed to protect us from being clumsy.
Dick,
I don't know why Snedeker wasn't told immediately that he was penalized. It sounds like a pretty clear case of this and there are decisions that directly say so. All I can guess is that the official on the spot made a mistake and it was corrected later.