Another example of this is the Python 2 to Python 3 transition. Python 3 is just too radical a change. Many features from it were backported to 2.7 to make the transition easier.
I think the Wave protocol had a similar problem. I decide to make an agent and just going through all the detailed protocol stuff discouraged me from digging in right away. I figured if it becomes big, I'll jump in again. On the other hand, I learnt plain-text SMTP as a kid and over time picked up MIME, TLS/PGP etc.
