Given that I've called Wave's doom from day one, I feel I have the right to comment once more on this silly undertaking.
First, even Wave's start was problematic. Google used the Wave announcement to suck the air out of an event Microsoft was holding on the same day, which was at best childish behavior, and personally I consider it unfair business practice.
Then, conceptually, Wave was a complete dud. Wave didn't offer even one interesting concept – seeing each others' keypresses is not a concept. That so many people got their knickers in such a twist over this shows just how banal and superficial the software world is, and why some of our best minds leave it in disgust to sell beer.
Technically, Wave was even more flawed. It threw out everything we've learned over the past decades in building internet apps, and replaced it with an ill-specified, unimplementable set of protocols that sent pieces of an extended form (!) of XML around, statefully and non-idempotently. Web-nativeness was an afterthought, and offline use wasn't even a consideration. That anyone took this crap seriously (hello Novell) is another sign of the shallowness that hampers progress in our field.
Every cloud has a silver lining. If there's one good thing about Wave it's that it showed that people long for new approaches to computing. Wave was like a Rorschach test, in which everybody saw what they wanted to see. In the end there was not much to see, and what was there was hideous. But still Wave showed that there's a possibility of introducing new concepts and having them adopted. If only someone found an interesting concept.
Long live the internet!