Don't want to go all tin hat here, but its worth remembering that big fences, lots of cameras and a bunch of seismic sensors in the ground are just as useful for keeping people <i>in</i> as for keeping people out.<p>Edit: I'm not implying an impending "soviet socialist state of america" or anything quite so slashdot, just remembering that there is precedent for Americans seeking asylum in Canada against what they felt were unjust laws at home.<p><a href="http://en.wikipedia.org/wiki/Canada_and_the_Vietnam_War" rel="nofollow">http://en.wikipedia.org/wiki/Canada_and_the_Vietnam_War</a>