There seems to be some confusion on this thread between magnetic resonance, which is the type of power transfer used by WiTricity and others, and radiative RF which is the radio technology we are used to. For example, received power does not fall off with the square of distance in the case of magnetic resonant systems. There are definitely a ton of challenges to this technology, but it is good to keep in mind that they are NOT talking about transmitting a high power RF signal and having it received at range. Here is a link to a paper that describes both types of systems so you can understand the implementation and trade-offs. The author's have achieved 80% efficiency over a few meters using magnetic resonance.
Experimental Results with two Wireless Power Transfer Systems
Video and other good info: