Facebook allows people to search out others by their email addresses – and won't let them opt out

Facebook is letting people be found with just their phone number – and there is no way to turn it off, according to users. The site collects people's phone numbers as part of a security setting, called two-factor authentication, which texts people when they try to login to make sure only someone with access to their phone can login to their account. Some users are forced to turn that on in order to use their Facebook, while everyone is encouraged to use it to keep their accounts secure. But Facebook is using those same phone numbers to allow people to look up others, it has emerged. And it offers no way of turning it off, even if people are aware of it and want it to stop.