My 0.02€ on what I read over here: http://scobleizer.wordpress.com/2006/03/27/second-life-is-an-os/
Being a "Platform inside a Platform" may be true, but then again every MMOG might become an OS. I for one am an avid player, as much as time allows, of EVE Online.
We have a player driven economy there, we have player owned structures, we have player run starbases, we have a ingame radio channel, we have out of game lootshop for ingame items/cash.. the list goes on.
Everybody is free, completly.
Given enough time invested we can recreate every situation we want.
But then, there is a red line, maybe THE red line.
All in all our online lives are entrys in a database, our characters, our ships, our assets. Everything can be reduced to a line in a table, referenced by or referencing to other lines in other tables.
Summing it all up:
We have an interface of medium complexity:
some mouse clicking, menues to a maximum depth of 3, a very intuitive style of chosing the own actions
With this interface we accomplish very complex tasks:
Fullfilling sell/buy orders, Killing pirates/other players for interstellar kredits (isk), running our starbases, defending our territories, having a good time online alltogether, having fun
The output of such complex tasks on the opposite is very simple:
It's our beloved lines in the database.
So, what good is a platform inside a platform as an OS when it just increases the complexity to get simple things done?