I agree with the author's assertion of a problem, but this is really confusing. Both Facebook and Twitter DO have APIs. Granted the APIs are proprietary and subject to significant restrictions on acceptable use and functionality. However, providing even a full-featured API doesn't change the effect of the platforms owning a person's user account and persona, or their ability to suck people in to waste countless hours watching their ad targeting feed algorithms.
Only true decentralization of social graph hosting will really address the core issue of centralized power.