Two
From related link
" Most of the Special Ops missions may be played alone, but all of them support two player cooperative play in which two players can play together locally or online.[21"
Currently, only 4.
on split screen, no, on live, yes
yes
you cant
You can not play split screen on multiplayer. It also left me confused
You can only do split screen if the person you are playing with is with you.
You can't
You cant, you must do split screen
No, you may not play Split Screen!
Call of Duty: Modern Warfare 3 for Wii doesn't have split screen because the Wii doesn't have enough RAM to handle split screen.
no
no not possible
No. None of the Modern Warfare series have been 2 player online (aka. online split screen).