This is very true. I'm 20 and I've never used my personal email regularly and I'm sure most of my friends haven't either. We've always used MSN or AIM and more recently Facebook to keep in touch.
I'm a 30-somthing urban professional and almost no one I know still uses MSN or AIM. Tons of people use gchat and gmail, including people who used facebook first. Looking at my adium contacts right now, there are more people signed into gchat than facebook chat, only one signed into MSN and AIM.
My wife's friends are the same way. Sure, lots of them have facebook accounts, but all of her friends and business contacts, new and old, email and gchat regularly. She doesn't even have a facebook account yet and has no intention of ever setting one up.
In fact, I feel less pressure to use facebook these days than I did a year or two ago. I don't even go on it anymore other than when I'm working on apps that use the graph api. My wall is filled with stuff I don't care about and if I want to contact someone I email, chat or text them.
But at least here in the US, every incoming first year student at a university in college has to have an email, and receives multiple emails per day from professors, administrators, etc. Email is still a huge part of the current college infrastructure, that could change, but I don't see it happening overnight.
I still email occasionally but only when necessary. That's why I said I'm not a regularly user. My point is that I've never used email for friend to friend communication.