A very interesting question. Maybe authoritarian governments simply ask the telephone company — traditionally being government monopolies — to issue 50,000 new telephone numbers to allow signups? Or they hire people to stand on a busy street to offer a free can of Coke to anyone willing to receive a Twitter code on their cellphone? Or perhaps Twitter doesn’t require a telephone number in those countries?

You can literally bulk buy sims in russia if you visit certain stores and ask nicely, because there’s not much oversight and people selling sims don’t make much money, so this kind of side hustle is common.

It's really easy to get blocks of phone numbers these days, especially with the proliferation of VoIP providers. You don't need to hold on to these numbers for more than a day.

There are countless SMS services and it is a race of blacklisting the numbers they use.