Wired is walking Americans through the brave new world of the administrative subpoena:
With a federal official’s signature, banks, hospitals, bookstores, telecommunications companies and even utilities and internet service providers — virtually all businesses — are required to hand over sensitive data on individuals or corporations, as long as a government agent declares the information is relevant to an investigation. Via a wide range of laws, Congress has authorized the government to bypass the Fourth Amendment — the constitutional guard against unreasonable searches and seizures that requires a probable-cause warrant signed by a judge.
There is little disclosure as to how these are used. It clearly violates the 4th Ammendment. And the FBI proved itself incapable of limiting the use of such powers when it had them under the Patriot Act.