Your putt stops at the lip of the cup. When you about to tap it in, you notice it is still moving slightly and you mention this to your opponent, but your opponent says you only have ten seconds to tap it in. You cannot hit a moving ball, so you wait an extra moment, and then the ball falls into the cup, and your opponent calls a two stroke penalty on you for taking longer than ten seconds. What would a rules official say about this?
This actually happened to Denis Watson in the 1985 US Open. The rules official imposed a two stroke penalty, and Denis lost the tournament by one stroke.
My Opinion: The ten seconds should begin at the point where the ball comes to rest. If the ball is still slightly moving, the ten second rule should not have been imposed. You cannot say it is ten seconds from when the putt was stroked, some long putts take longer than that to get to the hole. Besides, ten seconds is nothing compared to how long it takes some people to line up their putt and then freeze over the ball. Maybe there should be a time limit for that instead, after all, that is what holds up the pace of play much more than the ten second rule.
Losing the US Open because of this is an atrocity, and one of many reasons why the rules need to be updated and simplified. The object of the game is only to hit a ball into a hole, so unless you love beaurocracy, there is little reason for the rule book to be over 150 pages long.