" taking it back is hard"
It's pretty near impossible when it's something the public buys.
"But White Space allows regulators to hand over some spectrum for a bit and then take it back - within hours if opinion changes. Those lobbying against it are more concerned that the people will refuse to give it up rather than concerning themselves with any technical problem."
Indeed it *WILL* cause problems and the new gadget users will neither keep the rules nor give it back.
This is a disaster in the making.