So , the list so far (If I remember the other posts ) :
- Server to server communication
- Lobby system
- A solution to the problem I described (Unnamed )
- File transfer (Not a priority , IMHO)

Did I miss something ?
Short list , but vital to not only MMO but Multiplayer in general.
Of course , we can all add stuff thats not nececary , so lets focus on what is really needed Anyone else ?