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
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.