The NSA engaged in domestic surveillance on a massive scale. It collected information on both foreign nationals and US citizens. It collected large amounts of data indiscriminately. It did so in secret, with little oversight. It did so with the collaboration of major telecommunication companies.
Sounds familiar? Perhaps. But what I am describing is project SHAMROCK, an NSA program terminated in 1975 that collected telegrams sent to or from the United States.
Arguably, the situation is somewhat better today, as the NSA is now under Congressional oversight and it has (supposedly) internal procedures in place to prevent the unlawful use of data that they collect. That is, if you believe their statements. But then, they made similar reassuring statements back in 1975, too, before details about SHAMROCK came to light.
The bottom line, it seems to me, is that governments have the technological means, the capacity, and the willingness to engage in large-scale surveillance of their own citizens. No guarantees against an Orwellian nightmare can come from futile attempts to limit these capabilities. The genie cannot be put back into the bottle. Only the openness and transparency of our political institutions can guarantee that the capabilities will not be abused.