Long before the days of of web based Instant Messaging like Yahoo/MSN and sites Facebook, the Internet was composed of text based tools, most of which were based on the Unix platform. There was Pine for email, Tin for Usenet groups and a couple of different communication tools. One was Internet Relay Chat (IRC) was I sparingly used. The other was called "talk". Talk was a Unix based program which allowed you to do Instant Messaging with a user on either the same or a different Unix system.
I used all of these tools during my college days. I used Pine a ton to email my friends. I used Tin to read and post Usenet posting. I used talk a ton as well during those days. My fondest memories are from using talk for I seem to get a lot of random people wanting to talk to me. I talked to many people (mostly girls too...how odd) and they became online pen pals. I talked to a few gals up in Canada and a few at my own school. While I have lost touch with most of the folks from those days, there are a couple of people I email occasionally to say hi.
These days, I don't talk to random strangers online too much like I used to. With so much identity theft and other things, most people are vary of just chatting up strangers in forums or instant messaging.
Yet, that doesn't mean you can't maintain friendships online. With Facebook, it's easier than ever before to keep in touch with folks who you may not see all that often.
However, even before the advent of Facebook, I had managed to maintain a friendship with someone in which communication was strictly via email initially and later by instant messaging. This person was a former co-worker of mine who only worked with me for a few months together.
After they left, we kept in touch via email and migrated to instant messaging later. We have only seen each other once in the past 10+ years (oddly enough not even near where we live). Despite only communicating by email and instant messaging, I count this person as a very good friend.
Lots of friendships are built in different ways and this may be my most unusual. Yet, I appreciate it greatly. After all, for friendships to be maintained, there has to be mutual efforts. The both of us have made efforts and for that I am glad.