I came across this concept of pastebins the night before flying out, while reading the arch linux forums. I was surprised that I have never gotten to this part of the arch linux website before, and also that I haven't even heard of pastebins until now.
It seems like a really useful idea (and it is by the number of people using it). I myself don't remember trying to share too many pieces of code through IM, although I'm sure I've done it before. There's a free version of a pastebin (the original, in fact) which anyone can use. You can also append a subdomain in front of the URL to make things more private.
By checking the recently updated posts on that site, I noticed that some people use it for entire essays. While I also write journal entries in a one-entry-per-line format, I think pastebins are much more suitable for text when the lines are short, e.g. code, configuration files, to do lists.
And in fact, I think I just found a pastebin which someone uses as a journal... Hehe. Aren't these things fun?