We have anti-lag disabled, lag compensation was added in Patch 1.3 for COD4MW. The game uses User Datagram Protocol aka UDP, which is a stateless connection. If the client's packets are dropped in the middle somewhere, due to latency, packet loss, dog ate your internet etc etc the server will have to work with the data it received. It doesn't necessarily have to be someone with high ping, it could be someone on a not so great wireless connection too. You will see them skipping or teleporting over the map. Not all high ping players suffer this issue. I will give you an example @@NITRO has a fiber connection coming in. He is from Australia so his ping is in the ~250ms neighborhood. I have never seen him skip or teleport. Yet, I have seen a player with 65ms teleport all over the map.
A high ping does not good player a make! Even with the exploits of a bad connection.