Do we need....?
Some of the following features can be provided at the cost of greater complexity for the infrastructure, the client, or both. Other features might be provided quite easily, but at a cost of performance. It might be that some features are needed for messaging outside the desktop, but not within it.
Security?
as little as we can get away with -- NoelWinstanley
Encryption?
no -- NoelWinstanley
Guaranteed delivery?
no -- NoelWinstanley
Guaranteed ordering?
no -- NoelWinstanley
Queuing of messages?
no -- NoelWinstanley
Transactions?
no -- NoelWinstanley