Nearly all US Exchanges impose daily trading bands on some products, namely the index products (CME, Globex), agricultural products and so on. In my opinion, markets are so stable these days, that artifically truncating price movement makes no longer sense. The Wheat move last week is a good example, in my opinion. Also, it's an U.S. phenomenon. Of course, politics will play a role here as well. European exchanges follow a more liberal policy. What do you think - should this policy be loosened ?