I think that it is possible (tho unlikely) for an alternative to Twitter to emerge but it would require: 1) All clients start implementing the "open" protocol

I think that it is possible (tho unlikely) for an alternative to Twitter to emerge but it would require: 1) All clients start implementing the "open" protocol next to the Twitter. So send each message twice. 2) Someone takes the Twitter firehose and screws it into the "open" protocol. You would have a bit of noise but you would then have a legitimate choice: "open" or twitter. If the number of people using the "open" alternative/protocol achieved critical mass you would have something. Maybe this is why Twitter is clamping down on clients. Undermining the popularity of clients prevents the first item. And Twitter would never allow anyone to use the firehose for this purpose. So, pretty unlikely.