Facebook is continuing to push its mobile-first approach as more and more users become mobile-only users. As means to this end, Facebook blocked desktop access to the social networking site for its employees. This forced them to use the mobile apps and figure out what's wrong with them.
Facebook Product Manager Josh Williams:
To be honest, a couple of weeks ago, myself and a number of other product managers had access to our website internally shut off. Basically it forced us to use only mobile devices for a week ... It forced us to say, 'Hey, we have these features that exist in one place but not in another, and we have to remedy.'
Facebook has previously forced its employees to switch from their iPhones over to Android devices to encourage development of the Android app. At the time, the Android app was far behind the iOS app in terms of performance, design, and overall functionality. This apparently worked well because the Android app of today is much better than it used to be.