I wouldn't appreciate split-screen in this game for this reason; this game is an objection based team game. A lot of communication is going to be needed for success. When people are split-screening, they 98.75% of the time don't use mics. and when you are playing with someone who doesn't have a mic, It gets frustrating.
but i guess this doesn't really have anything to do with the topic. haha sorry
That's for "on-line" splitscreen. The devs are talking alot about how they've blurred the lines between off line and online, developing the same characters in both, so having offline co-op or competetive splitscreen (even if it was only 2 player) would be huge and obviously wouldn't effect communication on-line at all.
Also, I've played CoD:BO on-line co-op and while we don't always use a mic there's A) the fact that we are communicating so you have 2 people on the same page at all times and B) we're always listening for communications from others. Teamwork is a mentality, you either have it or you don't and even if you don't have a mic it still works.
I would love split-screen, it's the only thing that's keeping me from pre-ordering it right now.
EDIT: Hmm, it seems it turned my point B into a smiley, oh well.