After the Guardian’s revelation that the National Security Agency is mining the data of Verizon customers on Thursday, some of my colleagues told me to settle down. Some volunteered to be spied on in exchange for reduced rates. I figured that the level of outrage would rise only if people thought the government had access to the actual content of their communications. But apparently I was wrong. The second shock wave about PRISM—the NSA’s program for vacuuming up online content including “emails, file transfers, photos, videos, chats, and even live surveillance of search terms”—has hit. And my Twitter feed and my email inbox are still filled with jokes and shrugs.

Why is that? To me, it’s kind of a mystery. I’m disturbed by all the secrecy—the secret legal interpretation of the Patriot Act that’s behind the court order to Verizon, as Noah Feldman points out, and the secret decisions of the Foreign Intelligence Surveillance Court, which approves almost every request for information it gets from the government. And I’m also with Rebecca J. Rosen, who traces the history of “security-state creep” and worries about how it is increasing. That’s what creep means, after all. She notes, however, that the Supreme Court dismissed a recent challenge to the 2008 amendments to the Foreign Intelligence Surveillance Act—the law that enables PRISM—because no one who sued could prove that he or she had actually been spied on.

Maybe that’s the problem. We now know the government has access to all sorts of our Internet data. But we don’t know whose has been targeted or what has happened because of the snooping. It’s not like the NSA is sending a note telling you to stop cheating on your boyfriend or even to shut down your cocaine business. NSA snoops are not all up in our business, as far as we can tell. The danger is that they could be. Once the government has access to all this data, it has untrammeled power over it—which it could abuse. How you feel about that possibility is probably a function of how much you care about privacy in general and government intrusions on privacy in particular, and how much you imagine that you’d personally be at risk if some NSA agent did actually read your email. If you think your life is already spread all over the Internet, and that the agent would only be bored by your mundane messages about work and whose turn it is to pick up the kids, then hey, you’re good.

But then ask yourself: What would it take for you to be disturbed by massive data trawling by government agents? What if a nugget of information unearthed through PRISM surfaced when the president was vetting a nominee for confirmation? What if the NSA used such a nugget to embarrass an enemy of the president? Would that be Nixonian enough? Or would it take a series of abuses before the public decided that the country had traded away too much civil liberty? I can’t tell you that what the government is doing is illegal. The government’s defenders are correct that Congress has given the executive the opportunity to use these powers, and that the executive branch has followed the process for judicial oversight, such as it is. But that doesn’t mean we shouldn’t dial back these laws now that we have a real glimpse into the full scope of their reach.

President Obama offered two reassurances Friday. “When it comes to telephone calls, nobody is listening to your telephone calls.” Right, except they’re scrolling through emails and online chats. Oh but wait, “With respect to the Internet and emails, this does not apply to U.S. citizens and it does not apply to people living in the United States.” Right, except that NSA agents only have to be 51 percent sure the target they locate in the mounds of data is foreign. Everyone seems to acknowledge that they will inevitably sweep in “incidental” information about Americans. And when they pick up “U.S. content” by mistake, we are told they will put it into a separate database and then “it’s nothing to worry about.” Yes it is, as Amy Davidson points out. And it is depressing to watch this president become a misleading parser of words in the service of arrogating authority.

The government has admitted to unconstitutional NSA spying before—last year. The existence of these newly reported databases should be worrisome because once the information is collected, it is so much easier for the government to misuse it. The more data mining, the more it becomes routine and the more tempting to come up with more uses for it. If you trust President Obama and his people not to go too far, what about the next president, or the one after that? We have now had a Republican and a Democrat administration sign up for a broad expansion of warrantless wiretapping and other surveillance, and bipartisan support in Congress for the tradeoffs we have struck. And yes, there is more to the current revelations than we know—in particular, the rationale for the FISA court’s long-standing order for the phone data, and the rationale for PRISM. Let’s concede that a terrorist attack somewhere has probably been prevented as a result of these efforts. So how do we ever go back?

We probably don’t. And someday, the abuses will begin, in all likelihood long before we know about them. I’m not usually moved by slippery slope arguments. But this one looks so very easy to slide down.