The purpose of protest, Russ, isn't simply to "express dissenting opinion". The purpose is to get the damn policy changed. That has never happened by being ignorable to those in power, or by letting them go about their business without interuption. It doesn't help that Bush never lets out just where he's going to be more than a couple of days in advance, and so it's nearly impossible to get a significant conventional demonstration underway in that amount of time. If he announced his visits a month in advance there would be thousands, if not tens of thousands, protesting him just about everywhere he went.