I've talked about it for sometime. Last year, I even had my students choose user names and everything. Next year, provided I find a place to work, despite what internet filters are in place, I will make this happen.
I don't think I'd use it in the same way Legaspi does here - it looks like all the discussion is happening on Twitter. Seems like it could be used in addition to classroom discussion, as a sort of background chatter that continues after class. And did you hear what Oscar Lorozia said about feeling valued and respected in the classroom.
Yeah, it's gotta happen.