Sometimes honest mistakes led organizations to invest in these technologies. Sometimes there's self-deception and mismanagement -- and far too often lobbyists are involved. Given the enormous amount of security money post-9/11, you inevitably end up with an enormous amount of waste. Transparency and accountability are how we keep all of this in check.

Second, we need to ensure that law enforcement does what we expect it to do and nothing more. Police powers are invariably abused. Mission creep is inevitable, and it results in laws designed to combat one particular type of crime being used for an ever-widening array of crimes. Transparency is the only way we have of knowing when this is going on.

For example, that's how we learned that the FBI is abusing National Security Letters. Traditionally, we use the warrant process to protect ourselves from police overreach. It's not enough for the police to want to conduct a search; they also need to convince a neutral third party -- a judge -- that the search is in the public interest and will respect the rights of those searched. That's accountability, and it's the very mechanism that NSLs were exempted from.

When laws are broken, accountability is how we punish those who abused their power. It's how, for example, we correct racial profiling by police departments. And it's a lack of accountability that permits the FBI to get away with massive data collection until exposed by a whistleblower or noticed by a judge.

Third, transparency and accountability keep both law enforcement and politicians from lying to us. The Bush Administration lied about the extent of the NSA's warrantless wiretapping program. The TSA lied about the ability of full-body scanners to save naked images of people. We've been lied to about the lethality of tasers, when and how the FBI eavesdrops on cell-phone calls, and about the existence of surveillance records. Without transparency, we would never know.

A decade ago, the FBI was heavily lobbying Congress for a law to give it new wiretapping powers: a law known as CALEA. One of its key justifications was that existing law didn't allow it to perform speedy wiretaps during kidnapping investigations. It sounded plausible -- and who wouldn't feel sympathy for kidnapping victims? -- but when civil-liberties organizations analyzed the actual data, they found that it was just a story; there were no instances of wiretapping in kidnapping investigations. Without transparency, we would never have known that the FBI was making up stories to scare Congress.

If we're going to give the government any new powers, we need to ensure that there's oversight. Sometimes this oversight is before action occurs. Warrants are a great example. Sometimes they're after action occurs: public reporting, audits by inspector generals, open hearings, notice to those affected, or some other mechanism. Too often, law enforcement tries to exempt itself from this principle by supporting laws that are specifically excused from oversight...or by establishing secret courts that just rubber-stamp government wiretapping requests.