I've never really understood the purpose of Pastebin from a practical sense. I think I get the concept, I just don't know why you'd use it. That being said, its darker side is breach data dumping for the world to see.
Yesterday, I was thinking about the API and wondering if I wanted to write a script to search the pastes for client email addresses. While digging around on the site, I checked out a few pastes. Lots of people dumping code snippets and then I saw something. Among the code snippets, I saw what looked to be base64. I grabbed it, decoded it, and what I saw looked to be binary gibberish. I thought it was going to be something clever like a message but that's just me playing too much CTF. But then I did a Google search for "What is the purpose of Pastebin?" and I saw a search result talking about base64 encoded malware. What!?!? After reading the article, I was left with only a partial picture. Perhaps the author didn't want to spell things out completely? I don't know. So I started working it through on my own.