Here's a video of a talk I always show my surveillance students about how revealing phone metadata is and how hard it is to use things like Faraday bags:
https://www.youtube.com/watch?v=BwGsr3SzCZc
There are two ways you might react after watching:
Unenlightened: Ha ha, look at the stupid bumbling CIA.
- or -
Enlightened: Holy crap, if actual trained CIA covert operators can't pull this off for a couple weeks in a friendly country, what chance do I have?