Take a look at an excellent extended essay about surveillance in the USA, by Glenn Greenwald over at the Cato Institute. From the piece, two brief quotes to demonstrate the applicability to the debate we're having here:
there is no surveillance power too intrusive or unaccountable for our political class provided the word “terrorism” is invoked to “justify” those powers.
the Surveillance State already collects so much information about us, our activities and our communications — so indiscriminately and on such a vast scale — that it is increasingly difficult for it to detect any actual national security threats.
True for the States, and true here too. It's well worth reading the whole thing - it's a researched and scholarly piece. You'll be struck by a few facts - for example,
Every day, collection systems at the National Security Agency intercept and store 1.7 billion e-mails, phone calls and other types of communications.
One interesting coda. Greenwald talks about the fact that post-9/11 unlawful surveillance uncovered by the New York Times was "immunized" by Congress in 2008, and that "that same Congress twice legalized the bulk of the warrantless eavesdropping powers which The New York Times had exposed." As we well know here in the UK, we have had "warrantless" covert surveillance for some time - and it's been in the hands of local councils, to boot. A pledge by the Coalition to enact a warrant requirement has, as yet, not been realised.
By Alex Deane