I used to use small airports when I was riding road motorcycles (quit that 10 years ago, wild life (not mine, but deer etc.) makes them too damn dangerous, plus my current Prius gets better mileage then my last Gold Wing, can haul more, etc.) and I needed an overnight site to camp. Already knowing how to do it from flying (SMALL airports, smaller the better, funky and out of the way places) and then just find some dead end spot out of view/out of the way and just do it. I never had any issue doing this, and if I was ever asked, my backup story (if on the bike, if in the plane, no excuse is required....) was going to be "I'm waiting for someone to fly in." The most important thing, and I'm sure the homeless are figuring this out, is what looks like a prime out of the way site during the day, can be terrible once the rotating beacon fires up after sundown! I can see others who have "been there" nodding their heads......and we don't even want to talk about the pop up sprinkler systems that can turn on at 2 in the morning (and 4, I once found out, 2 AND 4, had to move twice). It's a throw back to our barn storming roots, for we pilots anyway, and I am glad to report that it is still widely accepted, or at least ignored, in Idaho, Montana, and Wyoming anyway. No issues with homeless at strips here yet, though I did get a little PO'd one evening at a big motor home hogging the pilot's picnic table/campsite at Henry's Lake (Idaho), until I realized he may have been a pilot, using the same trick I did on my motorcycle, maybe he was waiting for a friend to fly in!