The irony of the email header collection is that since this batch of headers is associated with an "al Qaeda" investigation, then since the content of the emails is unknown, suddenly anyone who shows up in the headers appears suspect, especially out of context in a future datamine. Even though presumably hundreds or thousands of email addresses were in this same dump, and maybe one was of interest to the FBI at the time, but they cast the net as widely as they're allowed.
It's called "making the haystack bigger" in relation to finding the needle in the haystack. In other words mass surveillance increases the noise rather than the signal, which we've always know it does. The government just doesn't care because in the end mass surveillance allows it to target anyone at will without real judicial oversight for each person being investigated.
And this is where the rules/regulations become important for how many degrees of separation -- how many "hops"; see also the 'Kevin Bacon rule' -- they are permitted to pursue based upon the original source data.
If you believe that they actually adhere to them. As someone else described (I don't know), this particular collection started with "a hunch"...
If we don't know what our government and its agencies are actually doing -- to a reasonable degree, as it were -- we cannot exercise oversight and we cease to be a democracy (in the form of a republic, or otherwise).
