I have heard some people have lost friends with in MW. I believe the issue might be due to the region battle net is set to. it seem to reset when it updates so make sure your set to americas

There is also another thing, I don't know if it is just my account, but certain or some people seem to not see me on their lists but I see them. But usually there are other people to invite me in. I don't know if anyone else was experiencing this too.

Hey Shane,
this could also be to do with activisions friends and battle.net's friends. In game its better to have activisions