Last week Google sent me a Wave account and I've playing with it since then. I pretend to see how can it be applied to e-learning, which is my fulltime work (nothing to do with my freelance work). There can be an unlimited numbers of applications given the concurrency of Wave, for example, a geography class could be managed using Maps to give students an exact worldwide location, then add a YouTube video to see something about the country, with a few photos or an album with different thematics, not to mention the interaction of the teacher with the students, or the interaction of students themselves. Furthermore, you could add gadgets or robots with quizzes for the student to solve and, through the API, output the result to a database located on any particular server. Moreover, since gadgets (or a Wave) can be located (or embedded) on a private server and thus the privacy and security issue can be solved, since you can make a Wave private by adding only particular participants.
I've been trying to embed a Wave in my blog, you can see the result in an image I attached, but in order to see it working you must have a Wave account.
Embrace the wave of the future!