Working with publicly available metadata from Twitter, a machine learning algorithm was able to identify users with 96.7 per cent accuracy

Metadata equals surveillance data, and collecting metadata on people means putting them under surveillance.

An easy thought experiment demonstrates this. Imagine that you hired a private detective to eavesdrop on a subject. That detective would plant a bug in that subject's home, office, and car. He would eavesdrop on his computer. He would listen in on that subject's conversations, both face to face and remotely, and you would get a report on what was said in those conversations.

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Now imagine that you asked that same private detective to put a subject under constant surveillance. You would get a different report, one that included things like where he went, what he did, who he spoke to -- and for how long -- who he wrote to, what he read, and what he purchased. This is all metadata, data we know the NSA is collecting. So when the president says that it's only metadata, what you should really hear is that we're all under constant and ubiquitous surveillance.

What they are trying to say is that disclosure of metadata—the details about phone calls, without the actual voice—isn't a big deal, not something for Americans to get upset about if the government knows. Let's take a closer look at what they are saying:

• They know you rang a phone sex service at 2:24 am and spoke for 18 minutes. But they don't know what you talked about.
• They know you called the suicide prevention hotline from the Golden Gate Bridge. But the topic of the call remains a secret.
• They know you spoke with an HIV testing service, then your doctor, then your health insurance company in the same hour. But they don't know what was discussed.
• They know you received a call from the local NRA office while it was having a campaign against gun legislation, and then called your senators and congressional representatives immediately after. But the content of those calls remains safe from government intrusion.
• They know you called a gynecologist, spoke for a half hour, and then called the local Planned Parenthood's number later that day. But nobody knows what you spoke about.

Sorry, your phone records—oops, "so-called metadata"—can reveal a lot more about the content of your calls than the government is implying. Metadata provides enough context to know some of the most intimate details of your lives. And the government has given no assurances that this data will never be correlated with other easily obtained data. They may start out with just a phone number, but a reverse telephone directory is not hard to find. Given the public positions the government has taken on location information, it would be no surprise if they include location information demands in Section 215 orders for metadata.

In a crime case, investigators don't have access to "the truth"—the data, if you will. All they have are clues which can be put together to make as perfect a guess as possible as to what the nature