This is a really clear and informative interview with a really impressive person: Edward Snowden, the PRISM leaker, a 29-year-old NSA infrastructure analyst employed by Booze Allen Hamilton. If there was ever any doubt about the gravity of these issues and the urgent need for public accountability, you should hear the case directly from him.
The total surveillance system that has continued its development under this administration provides the government with unprecedented power and knowledge about everyone, power which will continue to grow exponentially as Moore's law allows for ever-greater information storage and processing capability. These systems are dangerous not only because they can be abused today, but because they enable incredible abuses and retroactive violations of privacy arbitrarily far in the future. As Snowden explains, it essentially allows any authorized personnel, which included him, to bring up this stored information from far in the past to target anyone.
To state the obvious, I don't think any of the denials by the internet companies are believable. First of all, Snowden has put his safety and freedom in significant jeopardy and certainly sacrificed a highly lucrative career in order to bring his first-hand knowledge to light, along with the documents he provided to The Guardian. Maybe there is some nonstandard definition of "direct access" and other phrases that are being used to make these denials, but the Washington Post reporter Barton Gellman has said he's talked to multiple people who personally have exercised this remote, automatic access to the data held by companies like Google. Anyway, its obviously illegal to divulge a classified program, so any of these official denials are arguably compelled by the law anyway – or at least by the power of the legal system – and of course its strongly in their interest to make them for all kinds of other reasons.
All of us who were awake during the last decade have seen how vulnerable our rule of law can be when a crisis hits and politicians and media alike start singing their predictable slogan, "We must do more!" As if no legal or moral principle is too important to eventually sacrifice if danger doesn't just vanish from this world. Programs like this quite simply should not exist because they represent, in Snowden's words a "turn-key tyranny", and the fabric our our system should not be predicated on trust in such broad powers exercised in secret.
Either way, its hard to argue that something like this will ever make a decisive difference in preventing a major attack. Any group that has the ability to launch a serious effort would certainly be aware that these programs exist, and so would know to avoid vulnerable communication channels.
As long as this guy is putting everything on the line to do what is necessary to protect and inform the US public, I think we owe him our moral support.