The interesting bit of Wave wasn't the product but the underlying framework components they created for it e.g. salmon protocol and the pubsub system.

They made many of the components needed to create an open source federated social networking system where separate implementations could interact with each other. So for example your user on your company's twitter/fb hybrid could have threaded conversations with other users across other organisation's fb clones (obviously with access control).

This could have been exactly the killer functionality to topple centralised proprietary Twitter and Facebook. Google should have thrown everything into it, could have turned out as impactful as hypertext.