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.

On a semi-related note, one of the interesting parts of the Xanadu rule set was this:

Permission to link to a document is explicitly granted by the act of publication.

> Permission to link to a document is explicitly granted by the act of publication.

No one thought that you needed permission to cite someone else's work before the intertubes.

A link is an actionable citation, but the action is under the complete control of linked-to site which presumably owns relevant rights to the document in question.

The Xanadu versus HTML choice is more complicated than the number of innovations. The Xanadu vision made you buy into the authors POV whereas HTML didn't.