While there would be arguments regarding having only a limited number of people on a TS (and above) project (such as OXCART), you limit the potential of information being leaked, and reduce the amount of tracing required if it is leaked. Using your example, 4 people (SR-71) is a lot easier to maintain confidentiality with vs 2500 (B2); otherwise there's an inceease risk of a repeating of the Thomas Cavanaugh or Noshir Gowadia affairs. No matter your stance on drones, they are the current trend and will be for some time, I imagine. From a cost and risk-assessment basis, they are a lot more appeasing than pilot-based aircraft. I've not had a crack at playing with consumer-level drones or remote control helicopers yet, the extremely limited flight time (5-10mins) kinda puts me off. That said, it will only be a matter of the time until the consumer grade ones weigh less, have further ranges etc. It will be even more intriguing when they start operating in autonomous union, too.