@JamesGleick This is really misleading, I'm sorry.
If someone particularly wants to hack your account, SMS is not a particularly secure second factor.
Twitter is recommending that non-paying users use free and much more secure mechanisms for two-factor authentication, not that they stop using two-factor authentication.
Twitter has done many really stupid things reently, and by "twitter" I of course mean Elon Musk.
But this isn't one of them.