“The American people have a right to know whether the NSA is conducting warrantless domestic surveillance of Americans in a manner that circumvents the Fourth Amendment to the Constitution,”
My guess is that this buying of location data is even one of their smallest violations in this regard.
For many years, the NSA has built entire data centers, just as normal companies buy single servers. Nobody should think that their total surveillance of the internet can (or wants to) spare their own people.