emails or email addresses?
I realize they are looking for contact information, but the article is probably in need of clarification.
If they are after EMAIL, then they are rifling through every last known direct and peripheral contact or note card or addressee of a person of interest. If they are using commingled emails and hand phone contacts, then this is where Google's in-the-recent-past mandatory synching is truly evil. On-the-go addressees in the hand phone get or got synched with one's gmail or related account. Old cruft i never WANTED in my android hand phone got shoved onto me. If the law enforcement agencies want that data, though, they'll get it, sycnced or not.
Think of this application: Visual Analytics and JMP:
This software I first noticed around year 2000. While it is deeply invasive in the authorized hands, it can be DEEEEEPLY invasive give its full power.
Money Laundering analysis is a particularly interesting area of this app.
Think you can hide behind proixies, anonymizers, and 250 routers, brouters, bridges and virtual networks? Think again.