RJ,
I completely agree with you. It's a move that shows poor sportsmanship.
I was playing a cheap set with a buddy, it was hill-hill and he was down on his second-to-last shot and I pulled the money out of my pocket. I was 15 feet away from him and not directly in his line of sight, but he flubbed the ball. I immediately knew that he had noticed me pulling out the money, so I swept the balls and handed them to him...and apologized.
To everybody who says that this shouldn't affect a person because others can play with chickens running around and loud louts around: This would affect me more than a lot of things because I have respect for my opponents. I respect them enough to expect for them to respect me and the game enough to not interfere while it is my turn. I can forgive someone who is ignorant, but once I've educated them, there is no excuse.
Great reply, it shows that you know proper etiquette, respect the game, and your opponents. Also sounds you like you would be a decent guy to shoot a few games with. The OPs whole point is not about being able to win while chickens hump your leg but about respect for your opponents and the game, something many players are a little short on. It sounds like he gives them the benefit of the doubt by telling them about their questionable tactics, it is up to the opponent what he chooses to do with this new found info and will show whether they guy is a dick or just simply did not know proper pool etiquette. Hopefully the quarter clackers become educated and pass this info along so everyone can learn to be a better opponent win or lose.