If Google Wave is successful, will anyone care about Twitter anymore?
To me the most exciting thing about Google Wave isn't that it's real time; nor that it's live; nor that it combines email, IM, and social networking; nor that it lets people send photos quickly; nor that it is the first "web application" that has genuinely resembled a desktop app (drag and drop photo uploads!); nor universal editability; et cetera et cetera et cetera.
Nope, it's that Google must have some crazy data organization tools to make the whole thing work. For example, the natural language processing engine underlying the whole thing. I'm sure there are countless other technologies.
If Google's serious about moving the conversation into the internet age, and replacing our current snail-mail analog with something revolutionary, then delivering relevance is going to be key. I don't want to see the most recent emails at the top of the list, I want to see the most important. Or the most interesting. Or the ones regarding my family. Or the ones from my family containing pictures of vacations. Show me the tools to organize my content and I'll show you a winning paradigm.