I work Syncplicity, a Dropbox competitor and investigated building a feature that is similar to the Dropbox badge. (We call it the App Tab. Basically, it's UI that tacks onto Office that tells you that someone else is editing the same document.)<p>We've had requests for this feature for years. I can't stress how much customers request this feature; it's put a lot of egg on our face that Dropbox beat us to it.<p>In order to do this on Mac, we'd need to register ourselves as an accessibility client. I don't remember the details about registering ourselves, but from what I remember, it doesn't require hacking into OSX.<p>We've had to hack into OSX in the past: Adding menu items and icons to Windows Explorer is supported via well-documented Microsoft APIs. It wasn't until about 2014 that Apple supported this, prior to that, we had to reverse-engineer Finder. We didn't get OSX APIs to do this until we hired a contractor with "connections" to Apple he petitioned his connections to provide an API. I know that Dropbox, Google Drive, Box, and an open-source project called Liferay-Nativity all performed the same hack.<p>Based on my Syncplicity experience is that, what happens in these cases, is that a product manager gets so focused on the pixels that he/she is completely blind to the practical implementations. There's probably a bit of "I told you so" coming from some of Dropbox's engineers now.