Anyone want to brainstorm options on this? If the phone auth is to prevent the possibility of creating spam accounts at no cost, is there anything else we could do?

Piggybacking auth on top of existing services that go some way towards limiting registrations already is an obvious option, but not an attractive option. I can't see many people wanting to link their Steem and Facebook accounts, for example.

10-minute clientside proof-of-work validation?

Any other ideas, folks? :)

(EDIT: Aside from switching to a different outgoing SMS provider, of course)