@aral @mulander what they always try to do if an open system gets popular enough is:

• Create a supernode and attract users with offers, games or enticing but ultimately elusive revenue models (like Adwords)
• Slowly an as unobtrusively as possible add proprietary extensions to the protocol so that users can be captured on the supernode and can't easily just move to another server. Claim it's all in the interests of "innovation" and "user choice".
• Declare the original system to be obsolete and deprecate the original protocol in favor of their proprietary one.

Embrace, extend, extinguish. It's tried and tested, and it works - at least sometimes.