My friend sent me a concerning message saying he had been deranked. I check his rank and it was Lvl 54, 0 prestige. He then went offline and came back on and his rank was lvl 1. He told me that whilst ingame everyone was lagging then the server disconnected and he had lost everything.
Now that is pretty bad. Treyarch has made a good game but with all the little things that are happening including, lag, disconnections from servers, Ps'3 freezing every 2 minutes etc. People may doubt that.