People should also know that Firefox (and Thunderbird) collect _quite a bit_ of information about your interaction via their telemetry mechanisms.

Here are instructions on how to disable all of it:

https://github.com/Aetherinox/firefox-telemetry-block

(and no, you can't do it with just a few checkboxes in the prefs, you have to go into the advanced pref editor and look up some stuff.)