It's technically illegal to fly UAVs without visual contact in visual flight rules air space.
The FAA controls the national airspace with a white-list approach. Everything is illegal unless a specific category of safe flight has been defined. AC 91-57 defines the Model Aircraft Operating Standards and creates a specific legal exemption for vehicles flown for recreational purposes. This exemption also applies to UAVs, provided they are flown for recreational purposes. However, there is no exemption for operating a UAV for commercial purposes. Even flying an R/C aircraft is illegal if the operator attaches a camera and attempts to sell the resulting aerial imagery!
The FAA recognizes that people and companies other than modelers might be flying UAS with the mistaken understanding that they are legally operating under the authority of AC 91–57. AC 91–57 only applies to modelers, and thus specifically excludes its use by persons or companies for business purposes.
-- from FAA–2006–25714, Unmanned Aircraft Operations in the National Airspace System; Notice of Policy; Opportunity for Feedback (FAA link to pdf is down right now)
Technically, you or I could fly a 1:1 scale F-22 Raptor, but only if it were for recreational purposes.