Independence (population 9,846 at the 2000 census) is at the high end of the 5,000 - 10,000 range, so Cable One is able to make ad insertion work financially with current technology.
My point remains, however, that Google's plan (or rather my version of Google's plan, which may or may not be Google's version of its plan) will reduce ad insertion costs dramatically. If costs drop as much as I think they will, I'd guess that even cable systems with as few as 50 subscribers could make the numbers work. That also puts it within the range of affordability for MDU complexes and mid-priced motels.
Neal McLain