more than 10 years ago, most of my friends are on ICQ and YM, few on MSN. nobody on gtalk and facebook (well to be fair, facebook did not exist yet and gmail was fairly new and you need to be invited). now everybody on gtalk and facebook, few still in MSN, and nobody on ICQ and YM.
are there still people on ICQ and YM? i still keep my account online using instandbird and imo. just thinking of ditching it because nobody ever online there.
ICQ is still used in some projects as a place where people join to collaborate an support. As an example drupal project.
To meet friends social networks has totally replaced a simple chat app. From the social networks Facebook and Google+ are the most used, and we shouldn't forget Twitter (there is a lot of interaction through twitter too). And probably there are some more networks with a good amount of users, like tuenti.
Lately the mobile instant messagers has gained a lot of activity too: whatsapp and all the each time more and more like apps, as line, spotbros, tango, ...
I would even say that whatsapp can soon, if not already, go beyond social networks as the instant messaging tool. Though still can't replace social networks for every task.
My sister used to use ICQ a lot when she was in high school. My brother used MSN and even I got into MSN and my sister had to hop on that band wagon because ICQ was getting a little old and MSN was the new thing. I'd been using MSN for years but it was after my last school term ended (last year) that I noticed no one was ever on MSN anymore. I end up talking to a lot of my friends through Facebook. I ended up downloading Facebook Chat so I didn't have to worry about accidentally closing my browser and the chat. I never found gtalk went anywhere... None of my friends used it and I can't stand to have it running on my computer int he background since I have a handful of mobile devices that will go off if I get an email.
I haven't used Skype for phoning. But have for messaging. Only for the last week or so since it has become "legal" in the UAE to use. I haven't had any problems so far however. I also was more than OK with WLM when it was still a going concern.