Quote Originally Posted by chocomaid View Post
snip
Since I wanted to keep the original post simple, I avoid listing out the logistics of the system. I'm sure they could figure out an elegant method to implementing this general idea. For example, they could allow for cross-world adding to your friend list and blacklist and simply make players on your friend list preferred and players on your blacklist blocked. In the case of your last example, if they can't find another way they could at least make the players on your blacklist/blocklist -least- prefered over other players.

There are already systems like this in place they could pull from, like XBox Live I believe.