Communication on the web and evolving fast in diverse forms.  Collaboration, meanwhile, has fewer variants; it's mostly about editing content together.  True, there are many ways to collaborate on content (simultaneous editors are making strides), the variety of content is growing beyond simple text (online spreadsheets are blossoming), and the great communication tools facilitate all sorts of collaboration at a distance.  But -- with important exceptions like Second Life -- when people are building things other than content, chances are the creation isn't happening live on the web in the Wiki Way.