How can one prevent the state power from simply eliminating the witnesses?
The network would very rapidly notice whenever a witness stops posting units. Since witnesses are publicly known, they can be contacted, and if no satisfactory explanation is given (or the problem is not solved) the community at large will decide to replace that particular witness address for someone else's.
So no matter what the state power does, or a hacker, or just a witness turned malicious by himself, Byteball is not vulnerable.
So in that sense I'd argue we don't even have to "trust" these witnesses.
I see it from the perspective of a simple consumer. He certainly does not feel assigned to any "community". He expects his money to be safe and transactions to be handled reliably. If his witness (presumably the one who is preset after downloading the app) fails, he probably doesn't even notice it consciously. Result: nothing works anymore => panic.
A concept of randomly rotating anonymous witnesses who would route their technique over Tor/i2p would be much more convincing and above all safer. Especially as EVERYONE can be a witness to this. To get a permission from the dictator before would not be necessary at all. - That would be real decentralization.
Bite ball started out very promising, but the really important developments will be neglected.
Months ago I stopped my efforts to bring this project forward. One does not make friends with his customers.