Earlier quoted context omitted.
> There is nothing inherently wrong with centrally stored data. I'd argue that a 3rd party having the personal details and communication logs of 2 billion people is a massive problem. Privacy, governmental data requests, accidental information leakages, profiling, job applicant scrutiny, fake news, spam, data misuse by employees etc. Or even worse, in times of war.
What does this have to do with centrally stored data. Having data in a central store doesn't imply third parties. If the store is decentralized, then any party could be equivalent to a third party, and therefore anyone has access to your data.
If Alice wants to communicate with Bob, she shouldn't be obliged to trust Facebook too.