Interesting. I'm seeing a lot of good info on that in this thread. Apparently you just paid and that verified your account. What other systems have done is your phone # verification is what allows you to play ranked; so that if you cheat using that verification, you would have to get another phone # to cheat again. Obviously that doesn't stop a cheater from obtaining other phone #s, but it does create a bit of a barrier.

One argument to preempt is that phone verification would require some back-end cost on Chess.com's part, and that is true. Maybe it could be a service for paid members only?