I got rid of my cell phone number 541-913-2328, which has been my AT&T driven identity since 1999. I'm not doing much traveling this year, so having a $100 / month bill for a thing, that sits in the corner made no sense. Honestly, if feels fucking great not having, but that is another story. Beyond it feeling good, in the wake, I'm noticing how much our phone number is kind of the SSN for our digital identity.
Facebook, Twitter, and all my networks use this as the defining data point of who I am. The platforms which I use to define myself online, almost all use 541-913-2328 as the identifier that I'm real, and not just a bot (wait, am I?). I can't sign up for another phone number with Google Voice or Twilio, without well, an existing, valid phone number. It all feels like the same chicken and egg thing we face around regular forms of identification, well you can't get your drivers license, passport, without two forms of existing ID--wait I need that ID to get other ID, then I can show you!
In the pantheon of data points that are used in the world to identify that a person is a person, and they are the person they claim, I'd say the phone number is now in the top 5. You aren't anyone in a digital sense if you do not have a cellular-equipped device, attached to a nine digit phone number. That data point is key to services like Facebook, Twitter, Apple, and Google. It is how you will message, make payment, and engage with people on a personal, and professional level--acting as a critical data point that helps identify both our physical and digital self.