A massively decentralised protocol would not exactly be the model of reliability, either. I'm not even sure how that could possibly work in a service like Twitter.
It would probably work like an IRC network. A network might involve hundreds of servers, but you only notice which server another person is using when there's a netsplit. Split users can reconnect using another server and rejoin the channel with only a slight interruption.
An IRC-styled Twitter would need some sort of synchronization service to handle twitsplits.
Note the irony of this comment existing in a post about the service not being accessible, anywhere. Which wouldn't be the case had it been a protocol.