To address a couple of the places mentioned in one of the links above:

The "camp" at Ft. Stanton, New Mexico is a minimum-security lock-up for juvenile offenders on the grounds of an old Indian bording school. It is small, ramshackle, and has no fence around it. Holloman AFB hasn't been "taken over" by the German Air Force (aka Luftwafe), but the Germans do a lot of training there...there isn't a lot of empty territory in Germany to do high-speed, low-altitude flying. They pay their own costs, so why shouldn't they do construction if they want to? I was at Eglin AFB last month. Yes, it's big, if you include the satellite facilities...so what?