Scott Horton agrees that the NSA-Stasi comparison is inapt, but notes that it can have a cautionary relevance:
East Germany was indeed a surveillance state, but it was one in which the power and authority of the intelligence services to spy on their own citizens rested on an elaborate network of laws that empowered surveillance and eroded the rights of citizens specified in the country’s constitution. The detention of citizens was subject to strict legal regulation, and long-term imprisonment rested on decisions taken by courts. As is the case in many nations, matters that involved sensitive national-security issues could be tried in secret by special courts (the 1a panels of the Bezirksgerichte), but long-term detention required a criminal conviction. The conduct of Stasi officers was also subject to careful regulation and discipline — there are, for instance, no documented cases in which Stasi officers physically tortured detainees using such “enhanced interrogation techniques” as waterboarding and forced standing, which were approved and employed in recent years by the American intelligence community.
This isn’t to say that the Stasi was any less loathsome, only that it operated under the strictures of a highly formalized legal system. This system ultimately bent to allow increased Stasi surveillance, and the rights of East German citizens became ever more ephemeral. This is not the reality of America today. However, the Stasi’s evolution does reflect the corrosive effect a powerful surveillance apparatus can have on legal institutions — in other words, it reflects what America (and Germany) must guard against.