I recently added a paste-bin to the site (like the world really needed another one?). I felt like the other ones were missing a few features, and I wanted to see if I could do it. The editor is powered by Ace Editor, so syntax-highlighting, code-folding, and a lot more features are built right in (no code-fold on the viewer yet).
Replies are listed on the side of pastes so you can follow the 'conversation', and parent-pastes or the 'replyto' is linked on the page to help with the conversation also. If cookies are enabled it will remember the last language you used, and what your name is (what you typed in the 'Author' box).
No login/authorization is required. Who wants another login right now anyway? I did however, put a public api in place so pastes can be retrieved in JSON format. So if anyone wanted to write a piece of software based on this paste app it wouldn't be hard at all. Just read http://welbornprod.com/paste/api?id=latest and parse the JSON response. You can list the latest pastes, sort them by most view counts, and of course you can view a single paste by passing it's id in the 'id' argument.
Maybe in the future I will get around to adding more features, but I'm still proud of it as it is. What more do you want out of a weekend hack?