Facebook has achieved many good things but has also broken the trust of many people. By breaking our trust, they became rich in the process. Now that privacy issues are arising all the time Facebook is looking to clean up its act. Maybe that's the real reason why Mark Zuckerberg is investigating encryption possibilities.
You couldn't explain better the reasons, the trust, it's worthless that when it gets lost it's difficult to return to its original state, leave facebook, just before entering steemit, just because it wasn't pleasant for me anymore, then came all these scandals of privacy violation that simply don't encourage anyone to return, however I don't compare steemit with facebook, they seem to be different concepts, where steemit is consolidated in originality! I bet on the growth of steemit with greater popularity than facebook, so Mark will have to reinvent himself to recover the hearts of many, mine is already steemit.