You can (as we see) knock up a bare bones copy reasonably easily. The expertise is already out there. I'd say quite a lot of people are working on realtime collaborative comet stuff, and have been for quite a while now.

The hard bit is getting people to use it.

I wrote a fun multiplayer drawing applet (Java) back in 2000, but no one used it :( sob. Actually a few did, it was fun anyway :) One of my points is, this technology is nothing new.