At my school Google Talk ("gtalk") was as popular as Facebook chat. It is still used, but I personally prefer FB chat (for convenience). Not many people from my high school have a Twitter account, and many still don't. Even fewer use it regularly. I do see more and more friends using it though. I only use it because I'm involved in the tech scene. Quite a few people have Instagram accounts (about a third of my FB friends), and use it frequently. The only shift I see going on is that more of my friends are posting photos on Instagram than they used to on FB. But everything else gets posted on FB.
Maybe some of this truly is due to a difference in generations (only a couple of years).
It was 8 years ago when I was in high school, and back then everybody used AIM (AIM profiles anyone?). And before that, kids in the 80's used BBS's. I guess kids today use 'gtalk'.
It seems teenagers at a certain age just really want to be able to talk exclusively amongst friends, away from parents and prying public eyes.