Although two-factor authentication (2FA) is provided in order to protect your data, Facebook's implementation could actually weaken your privacy settings.
Facebook users can utilize 2FA by pairing a FIDO U2F hardware key, use an authenticator app to generate single-use codes or even have Facebook send those codes to them via text messages.
This last option should be avoided. As reported by TechCrunch, if you set up a phone number to use with Facebook's two-factor authentication system people will be able to search for you by that phone number. And your two-factor phone number may be hidden from your profile, but it cannot be hidden from other Facebook users, since it remains searchable.
Facebook has been encouraging users to set up two-factor to secure their accounts. But it seems that the company is also using a vital security tool for marketing purposes and for making social connections.