Your blog post is very interesting, replicated it in a game against some of my friends too. Very easy.
A friend of mine was responsible for scoring system on games. As they had some real awards (like bikes, tickets etc.) they captured the entire flow of the game with various statistics and later analyzed them for weird variations. That was in Flash and people used browser plugins to slow down the play, that was easy to spot. Of course it won't stop 100% of attacks, but it raises a bar sufficiently to thwart most attempts.