Centralizing communication really has more issues than just the "single company controlling everything" stuff.
Obviously having your whole communication depend on one single entity is horrible.
Comparably horrible is the notion that you have only one online identity, traceable, interconnected with itself and exposed to all your contacts.
In a world that forbids dropping your current identity you are forever bound by all your previous mistakes. You are easily undermined by your past opinions.
This goes well with the faulty concept that's being aggressively put forward about having to be consistent with yourself over time.
Best option (most fair one?) would be to both have people have traceable opinions over time and have society accept people's right to learn form their mistakes and change their opinions. That however is a pretty unrealistic utopic world.
People hold other people accountable for what they "once said" cause we love to hold a grudge and be superior to others.
You could have people overlook your past ideas and affiliations if they have first had enough conversations with you to assess that at this point in time you align with them ideologically.
That is however quite unlikely in a world where your first impression of someone is a complete timeline of all the stuff they've said/done/shared over most of their conscious life (soon there will be people over 18 who have spent their whole sentient life online).
And even if that is solved, people will still have the natural need to have fully unprecedented conversations, to explore changing their identity, ideology and ideas. To play with interesting alter egos. This is most prominent with artist type people, but normal people need this as well.
That's actually pretty much what people look for when they go to a random bar. A clean sleight to get to know people from scratch, to choose how to build your own image.