This is the way I wanted to play Onlinegames for a very long time. No people with dumb names hopping around in front of me ruining the atmosphere, no crammed dungeons or cities... I can decide whom I play with. And if I don't want to play with anyone, then I play solo. Even offline when I want to play with no internet connection at hand. This would be a huge bonus for Onlinegames, adding people as customers who don't want to or cannot play online.
As TESO wants to combine solo-player fun with onlinegaming by having quests that can be played solo why not have a similar selective-multiplayer-system? Why not give me the option to play solo if I want to? If I want to add a few friends or all of the players so be it. But it would be great if I could choose how I want to play the game. Therefore Selective-Multiplayer seems to be the next step in onlinegaming.