I stealth camped pretty much everywhere on my first bicycle trip across the United States this last month. I never really had any major problems besides swarms of musquitoes and other insects, and getting rained on occasionally. I've camped behind rest areas, in the mountains, behind churches, underneath church canopies during storms, in peoples' backyard, wherever there is shelter or seems safe enough.
My second night of the trip, I did have a strange incident happen. I was about 30 miles north of Santa Fe, New Mexico in the mountains. Had just set up camp behind a bunch of trees off the road and it was dark. This truck rolled by me super slow and literally stopped on the side of the road, flashed its brights. I could not see who was in the vehicle from my vantage point. After about a minute, the truck took off and thankfully, nothing ever became of it. Who knows, really. Could have been somebody called a rancher friend after seeing me, could have been they wanted to make sure everything was alright, or maybe they really were up to no good. I was on state land. Its hard to say.
But yeah, stealth camping is the way to go, especially on budget. Safe journeys!
Here are some links to my videos so you can see how I camped:
http://www.youtube.com/watch?v=PCf-US5moJU
_Jeff