I wanna give a nice idea to Killer Instinct.
In Ultra Street Fighter 4, the game ask you after every fighting if you wanna add your opponent or just move ahead, I think It is a good feature, because the community become more unity naturally.
When you want add someone in Killer Instinct that you played, you have a trouble, it is hard, you need to memorize the nick name of your opponent, so it isnt estimulate people to add each other e make new friends inside the game.
After a match,you can click Rb(I think) to open up their Gamer Profile. Add them from there.
Or you can double-tap the Xbox button in the middle of your controller to bring up the Xbox Guide. From there, go to your friends list, switch it to show recent player, go to their profile, and add them as a friend. 
I didnt know about this. Actually I tried and I didnt get it. So the game need a mechanism more explicit, and easy to use. For all kind of player levels can use that.