I'd like to suggest that the Badge be a different color when someone is using a file. The problem with the current Badge is that another user must make a proactive action (click on the Badge to see if someone else is sharing the file), and in most cases I (and other users) just save-and-close creating conflicted files.
Blue (as now) is great, for example, when I am the only user. If someone else access the same file, maybe red (danger) would be a good color. The both the first user andthe second user can be aware that a conflict is about to result -- at which point, one of us can log out without saving OR a phone call would determine the next best step.