This is cross-platform, which inotify isn't. Also, isn't inotify pretty low-level? It looks like FB has consolidated common inotify helper code into a reusable daemon.
http://people.gnome.org/~veillard/gamin/ has been doing this for ages, with inotify on Linux and kqueue on BSD. It's already packaged and available - indeed, often required - on many distributions. Facebook has done some neat stuff here, but providing a portable file-change-notification library isn't novel.
