Simple taxonomy of electronic media

With three permissions we can characterize eight forms of communications.
It is assumed that the user can read all messages. The other permissions are:

• user can write x--
  
• world can read -x-
  
• world can write --x
  

000 is a private read-only file
100 is a private writable file
010 is a public read-only file
110 is a write-once blog like Twitter
001 is email inbox where user can't edit messages
101 is email inbox where user can edit
011 is ???
111 is a Wiki

Google Buzz is like a Wiki.
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