A lot of people are freaked out by the idea that the NSA has for years been collecting data from ordinary Americans' email accounts. Nobody likes the idea of the feds combing through their email.

But experts know that it's not the content of individual emails that is the most useful thing to authorities. Rather, it's the metadata.

Metadata is, literally, "information about the information." Email metadata provides a much broader view of patterns between users, and who is communicating with who, than the text inside any individual email would.

If you want to identify terrorist networks, the metadata is what you really want, not access to the inside of a few suspects' accounts. (Although that might come later, of course.)

MIT has been working on a project called "Immersion" to let you do exactly that with your own email, so that you can see who your closest "collaborators" actually are (and not the ones you'd like to think they are). You sign up at this web site, and let the software arrange your email history into a visual network of the people you communicate with.

It looks like something this, once it's done:

MIT's Immersion Project

Here's a video describing how the project works.

Hat tip to NPR.