Then again, there is the Tiny House movement:  http://www.fyi.tv/shows/tiny-house-nation

These folk are - among other things - trying to get zoning ordinances which require homes to be at least 500 square feet (e.g. 10 dtons) overturned. Right now, most tiny houses (most of which seem to be under 200 square feet) are built on trailer bodies, so that they are legally mobile homes. Of course, that often involves them in a whole other class of restrictions.