Call me crazy, but when was the last time we were worried about cruise missiles over DC? I realize that the US has less-than-perfect relations with some countries, but the Cold War has been over for quite some time now.
[1] - http://ardupilot.com/
I have to second what Second_Ender mentioned -- we are at a critical juncture where off-the-shelf components offer rather frightening possibilities. I love technology, but benign videos like http://www.youtube.com/watch?v=tMwSVDVJNWc&feature=youtu.be leave me deeply concerned about the future.