Wave was a dumb idea because it was not finished and totally separated from all the tools used today. The features in wave all belong in other tools, not clumped together in something that was less than all other tools.
For example annotating documents in the wave way. Very nice idea for google docs. Not good inside wave where the editor was crude. So a new feature inside junk, or a new feature inside a very good tool.
Also google has some off idea that we want conversations all glued together, and that is stubbornly shown in gmail where you have to look at huge threaded views instead of individual replies. This is fine for some but many businesses hate it and it mars communication. Luckily I read one of the new higher ups is finally changing that feature.
Finally the day I saw the wave presentation and I saw that in place character by character editing, I said, that's a developer toy, not practical. Just because something is possible doesn't make it useful! People hate the idea of that document editing playback too, how could they think that was a good thing? Another gee look what we can do, but is as desirable as acne! "this is an crappy great idea". That kind of playback is not really what people want. It's like someone spying on you as you type. Creeped out users.