The New Scientist has a story on the successes and failures of DARPA projects over the past fifty years. Technologies such as the internet and GPS stand out as commercial successes, and there are other successful endeavors that have less commercial applications. I think we are all better off without telepathic spies as the regular spies are having a hard enough time with conventional intelligence gathering.
Maybe if DARPA had worked on flying cars we would have them by now rather than only reading about the paleofuture. Hopefully the automated cars the DARPA encourages through their annual road race will lead to more commercially successful technologies. It seems that this type of public investment (or encouragement of private investment through award incentives) in innovative technologies does have some efficiency benefits compared to private investment. The efficiency gains are likely located in the institutionalized protocol standards and shortened time to deployment for network technologies.
In any event, hopefully we will soon have automated cars, which will leave more time for scaling walls in our news Z suits.