Wave isn't a social network. It's basically persistent IM/chatrooms, with history, that you can attach stuff to, including little programs. It's actually a real-time communications protocol; Google would have done better if they gave Wave and their implementation of it a different name.
I can see it being useful for people that have to collaborate on projects online. I don't see it as being a compelling replacement for anything other than mailing documents back and forth, or ad-hoc wikis and things like Google Docs. I've yet to see how they deal with simultaneous changes to items in a Wave or conflicts as you'll get over high-latency connections, such as satellite. It seems like they think that making something "real time" (which is impossible in all circumstances) will magic away sync problems and conflicts.
Email is kind of antiquated. There needs to be a way to keep email's openness without drowning the world in spam. One way is to get rid of email's relative anonymity and easy forgeability, of course. My favorite proposal is a requirement that a penny be put in escrow for one week for each message sent (perhaps to only apply to certain domains), payable to the recipient on demand, if the recipient finds the message annoying. Thus making spam and other "marketing" no longer free of cost. There should also be a unique message ID preserved in replies to make threading possible without relying on subject headers.
The problem is that Wave tries to fix too much. 90% of collaboration-by-email fuckups I've seen would go away if people could be bothered to use any number of online tools and would stop using fucking Office programs for everything. There's plenty of room for technological improvement, but most computer problems are caused by people hanging on to old, bad ways of doing things.
I haven't read a single good review of Wave so far from people who've used it, and review technology for a living.
