Facebook says they will send fewer emails

Hi [redacted], We're trying out a new feature to reduce the amount of email you receive from Facebook. Starting today, we are turning off most individual email notifications and instead, we'll send you a summary only if there are popular stories you may have missed. You can turn individual emails back on and restore all your original settings at any time. Thanks, The Facebook Team

I wonder what caused this change. I doubt it is just A/B testing. It must be a decision from higher up. Ref: email subject was Facebook will be sending you less email - learn why