When he was in Florida today I noticed the camera panned to one of his Service guys panning the area.. first time I've seen one zoomed in on purpose.
I don't see why this is far-fetched at all. As someone above said, it is just a numbers game. Out of all the people in the US there are plenty who hate Bush. Out of those who hate him, there are those who want him assinated. Out of those there are those who would do it, and out of those there are those who can do it. Actually I find it pretty amazing that there aren't multiple assassination attempts on every president.