Does anyone know how using empty/unused TV spectrum plays into this? Seems like you would have far better success since they would be able to penetrate walls and other obstacles better than regular Wi-Fi signals can.

I know there was some research being done at Microsoft at using this as sort of a long-range wi-fi network but short of an installation at their corporate campus, I haven't heard any news about it lately.

1: http://whitespaces.msresearch.us/ 2: http://research.microsoft.com/en-us/projects/knows/