From the
Mythbusters files:
WIRELESS PERFORMANCE
AFTER FEBRUARY 2009

FALSE at present.
Likely TRUE in the future.
There is a proposal from the FCC that disallows the use of wireless systems in the 700 MHz range, potentially as early as February 17, 2009. It has not yet been mandated, but it specifies that equipment in this range not be used after the DTV transition date. That could mean effective February 17, 2009 or over a specified transition period.
Because new users will eventually occupy this range - telecommunications operations and public safety operations – equipment in this range may become unusable over time.
Breaking News
Recent legislative action at the Federal level may delay the DTV transition date until June 12, 2009. Nevertheless, operation of wireless systems in the 700 MHz range (698-806 MHz) will eventually be phased out as part of this transition. It is recommended that concerned wireless system users check the FCC website or the Shure website for updates on the DTV transition.

Here are some helpful places on the Shure site where you can find more comprehensive information on: