You need an experimental license because none of the (still prototype) devices have received FCC approval yet. In theory, the use of the whitespace frequencies

You need an experimental license because none of the (still prototype) devices have received FCC approval yet. In theory, the use of the whitespace frequencies is already open to the public - if you had approved equipment. The rate that the FCC is approving experimental licenses has accelerated a lot in the past 9 months, and new deployments are rolling out much faster as some quasi-commercial gear has started going to trial. While it is difficult to say for sure when the first generally available radios might arrive, I've heard a vendor suggest the second half of 2012. That would be for enterprise gear though, it might take a couple of years before it was hitting consumer price points. The database issues shouldn't be a big deal.