Brian Fung for The Atlantic:
When Google hands over e-mail records to the government, it includes basic envelope information, or metadata, that reveals the names and e-mail addresses of senders and recipients in your account. The feds can then mine that information for patterns that might be useful in a law-enforcement investigation.
What kind of relationships do they see in an average account? Thanks to the researchers at the Massachusetts Institute of Technology Media Lab, now you can find out. They've developed a tool called Immersion that taps into your Gmail and displays the results as an interactive graphic…
Remember the partially tongue-in-cheek Paul Revere analysis? This is that single-person starting point in the analysis, using just one email account.
You can run Immersion on your own Gmail account to see what Google knows about you, and about who you know. Those with a real privacy concern (or a heightened level of paranoia) probably shouldn't use this tool because obviously giving any outside agency more access to information about you is a potential security concern. Most of the people who are most likely to be reading this blog would know that already.
For the non-nerds reading this, an additional tip: don't use online password strength checkers either. That's one step less secure than the dreaded Post-It note security breach.