Alternative to invite for protection from trolls

Habrahabr chose a root way to deal with trolls - they introduced a system of invites. And what if we go the other way: for each user to make mandatory confirmation of a mobile phone. Each user has a unique mobile number, so there should be no repetitions. A troll after a ban needs a new number to confirm the registration, and after several bans using the mobiles of the family , further registrations will become problematic for him.
The question of the confidentiality of phone numbers remains open and whether users will want to enter them. Although if we combine such an option with invites (from particularly distinguished users), then we get protection from trolls and the ability to register with normal people.