Google wave is pretty cool but it doesn't look like the Blockland community is too active on it. It's kind of like people wanted the beta when it was special and they couldn't have it, and now that they have it they can't really find a use for it so they don't use it.
In comparison, my second account has some of my real life friends on it. We've made somewhere around 12 waves in the week or so we've been using it (although the wave creation rate will probably wind down a bit) with several updates a day. It's basically replaced facebook threaded discussions.
I found out that it doesn't replace IRC at all. It's just another layer of communication, we still use IRC, Skype and Facebook on top of Google Wave. Whichever is more convenient for a particular type of communication gets put in there. Quick conversations move to IRC or voice chats on Skype. Facebook basically replaced email, so notes we have to leave for each other get put on there. Planning stuff (movies, barbecues, parties, etc) gets put up on Google Wave because it's extremely convenient to hold threaded discussions, be able to embed and annotate maps with each other, run quick polls, etc, all in one place.
I think it would be really neat if there was some forum software that used waves for the private messaging system. Of course everyone joining your forum would have to have a gmail account...
