Better be conservative!
"They already took away the 700MHz spectrum here in the USA, and the 800MHZ (we had TV channels 70-83 there!) spectrum is mostly unused by analog cell phones"
The 800mhz is unused by *analog* cell phones because everyone has digital phones. In most markets, the two 800mhz bands are absolutely full, depending on who uses the band either full with GSM & UMTS (AT&T usually), or full with CDMA & EVDO channels (Verizon, US Cellular, etc.). It's not unused by a long shot.
As for this whitespace -- I hope this is set VERY conservatively for what white space can be used! Rural areas don't have as many stations, but this just means people try to pull in stations from 50-100 miles or sometimes more -- these people are considered outside the station's service area by the FCC, but have no local stations (or at least not enough to get all the ABC, NBC, CBS, Fox, PBS, WB, and on digital subchannels maybe RetroTV and ThisTV), so they pick up stations they are supposedly outside the range of by popping up a large antenna. I personally get some stations from about 70 miles away, because locally I can only pick up PBS, WB, and Fox. I'll be quite pissed if some Microsoft thing starts broadcasting over my channels!