A single DMCA notice is relatively easy to deal with. Even though a startup owner probably "should" consult with a lawyer, you don't need to if the take-down request is clear and the material is either clearly infringing or not. There are gray areas, but they are rare.

A letter from the NSA is a completely different story. You definitely need to hire a lawyer, probably an expensive one. One NSA letter could easily shut down a small startup.