My business partner and I (often working from different locations) are constantly working on the same documents and trying to save our work at the same time. Result: lots of conflicted copies of files. I would love to have something in the Dropbox UI that allows us to see if another person is working on the file or has the file open. It would save us a lot of FLAME texting. We love each other but this is one thing that makes us want to kill each other.