Indeed I know we've seen blocks trigger the penality, but we haven't seen a movement out of the median.
We have on multiple occasions. Not with the sort of smarter algorithms that ArticMine discusses though.
I'm not sure I agree we can ignore miner optimization. Such behavior may affect the overall incentives. Transaction creators and miners are in a sort of conversation, with fees as the language. You probably can't understand one side of this conversation, or the conclusion of it, without considering the other.