==== privacy settings ====
  * Make sure your Facebook app doesn’t have microphone access.
  * Better yet uninstall Facebook app from your phone

Why? I have heard of situations where two friends talk about a car and then facebook started showing them ads about that car.

==== facebook stats ====
  * Facebook has close to 2bn users, posting over 100bn things each day.
  * The latest numbers can be obtained from https://investor.fb.com/financials/default.aspx -> choose the latest quarter -> Earnings Slides.
    * The Q3 2020 pdf -> slide 2 shows
      * The number of daily active users (DAUs) for the past 9 quarters.
      * In each quarter, the numbers are broken down into four regions.
      * For each quarter, it also shows the ratio of daily active users to monthly active users.