I think there's a good anthropology paper in all these different IM platforms. Look at it this way, if you have MSN, and someone else has AIM, you can't converse. So I think it's logical to start asking how social circles are altered by IM clients. If you are on client, do you start to drift away from those friend on another client. What if you are introduced to a new circle (new job, school et cetera), is there then a sort of peer pressure to adopt the IM client preferred in that circle?