The fcc has been re-allocating frequencies for years. The 800MHz broacast band (channels 70-83) dissappeared in the 80's to make way for the AMPS mobile phone. In June of 2009 the 700 MHz band (channels 52-69)was eliminated as part of the transition to digital television.

For those who are interested there's a (slightly-out-of-date) US frequncy allocation chart located on the right side of this page:
NTIA OSM Home

Refering to the chart:

Digital channels use the frequency bands that used to be occupied by channels 7-51. That's the lower UHF and the upper VHF bands. As noted above the upper UHF band has already been re-allocated.

Channels 14-20 have already be allocated as multipurpose landmobile/fixed/broadcast. I can see that happening to the rest of the UHF band also.

Channels 2-6 from 54 MHz to 88MHz are not really used for TV anymore. Some of this is already in use by other interests such as radio controlled airplanes.

Note: I've used the old channel references not the digital channel references. Digital channel 2 is NOT on the same frequency as the old analog channel 2.

Other countries made the decision to re-allocate the VHF bands since they are less suitable for digital TV. The US decided to re-allocate the upper UHF band becasue they could get more money for those frequncies.

'nuff said.