I can't imagine playing CK2 with a bunch of randoms on the internet...
A) It takes far to long to complete, what are the chances a bunch of strangers area actually going to be dependable and finish a game!
B) Play style varies immensely in the CK2 database, could you imagine playing a fun RPG style multiplayer keeping your dejure kingdom dejure purposely as this other guy is pretending to be ghengis khan painting the entire world....
C) Peasant Rush! If you played games like Warcraft, Age of Empires etc a standard multiplayer tactic was to do a peasant rush to kill the other players, could you imagine someone in game deciding to take out another player early on???
So to sum up, I see so many ways a multiplayer game could go really badly. So I refuse to play mutliplayer with random people I don't know, I stick to friends on Team Speak I have known and gamed with for a long time that I can trust won't peasant rush, and won't pretend to be ghengis khan and will enjoy a civil game.