I think it makes a lot of sense for Google to stop developing Wave.
I have followed Wave since the announcement at Google I/O with excitement. I have also tried to use Wave in a few projects, always with a feeling of – what is this about?
So it comes as no surprise that Google is stopping development of Wave because of little user interest in Wave.
I admire companies that can launch new ideas, test them, and kill them if the don’t work. Well done!
I also think that Google will have learnt a lot of useful things from the Wave experience. Knowledge they can put into other services.