[gwern]

> And 100% of the evidence was that they met at the same pizza place? There were no other indications?

It was enough for the guys supposedly in charge of protecting us to waste a lot of time staring at graphs. And the 'threat matrix' is full of even more shit than that; I refer you to "Secret without Reason and Costly without Accomplishment: Questioning the National Security Agency’s Metadata Program", Mueller & Stewart 2014 http://politicalscience.osu.edu/faculty/jmueller/NSAshane3.p... for that and other sorry details of 'the war on terror'. Seeing the sausage made is never pretty.

> In that case does it flag every single group of high school friends who regularly get pizza after school, or every group of co-workers who hit up the same happy hour a couple times a week?

No, I'm sure some racial and religious profiling was part of the special top-secret sauce which selected that particular pizza joint...

[imgabe]

I agree that's a problem. I don't think the issue is that this database exists. I think the issue is that there are people conducting a witch hunt in the first place. If they are that bad at finding terrorists, they'll misuse whatever information is available to them. The solution is to not give people the power to conduct secret investigations and trials etc. in the first place.