If we have learned anything from the failures of current IM systems, then we should naturally prefer that a new proposal for an IM system include the following objectives:
The IM system uses an open, non-proprietary, freely implementable protocol.
The IM system is based on a distributed network model, so that there are no single points of failure.
Users are free to assume the IM handles of their own choice.
The IM system is secure and safe from typical security hazards.