Don't forget the problem of tiny homes on wheels being stolen while their owners are out! I've read of that happening a couple of times.
They should have to be up to code, and the dumping sewage in the woods is outrageous. However, I believe the tiny homes thing is here to stay. After all, they are similar to trailers, which have been a housing staple for a long time. I believe that in the years to come zoning rules will be changed to accommodate them, and perhaps even tiny home parks (like trailer parks) will proliferate. Time will tell, but I think as the boomers retire and the job market remains bad, tiny homes will fill a crucial need. I could never live in the really tiny homes, and would never have one on wheels, but one about 500 square feet would be just fine with me.