Plus, you are now bound to a regime where decisions may be based on external factors. Like the owners. Don't know if this is true, but what if some big shareholders want a controversial account to be platformed. Again, no recourse.
Open democratic systems don't have the same problem. There may be other things like multiple instances with different characteristics, reply guys and HOAs, but that may be the price we pay for participating in a truly distributed system.
5/5