In the pursuit of instant gratification
I couldn't live without instant messaging. I can't imagine why it took Paulo to install an IM client a week, as it would be the first thing I install on a fresh computer. What I find interesting is the differences between people when it comes to their protocol of choice - it seems to be dictated partly by where you live and when you started using the Internet, and partly by the same criteria applied to your friends. If you've had access for a long time (which I'll be defining as before home access became a big market), ICQ is likely to be your preferred means of IM (particularly in Europe and Australia, a little less so in the US). If you got online some time in, say, the past 5 or 6 years, then you'll probably use either AIM (the US) or MSN (Australia and Europe).
The second group of factors is the location and the level of "techiness" as applied to your friends - there's no point using ICQ if all the people you know use MSN. Fortunately, I'm sure all of us here use multi-protocol IM clients, but I can see how annoying it would be to juggle two or three different programs if you have a mix of friends over different protocols. In my case, all of the people on my contact list use ICQ accounts, and all of them have been using ICQ from near the beginning (although not necessarily with their original UIN). Those people who are on my very small MSN list are those who happen to use more than one system. In terms of usage, ICQ is almost dead - only a mere few million still use it, and is completely dwarfed by AIM and MSN (and that weird QQ or whatever it is they use in crazy Asialand).
What do you guys think? Is your perception to IM usage similar to mine? How is the distribution in your list?