Phone number reuse is also a major pain in this scenario. If your mobile phone number has ever changed, you still likely have the old number registered with man

Phone number reuse is also a major pain in this scenario. If your mobile phone number has ever changed, you still likely have the old number registered with many sites. The SMS you received may not have been for your Facebook account, but rather for someone else's account using your new phone number that used to belong to them. The number of sites that use - sometimes even requiring - SMS as a backup authentication mechanism, even while you use a separate authenticator app, is astounding. Cell phone number recycling is just as bad as email addresses.