Facebook already allows you to share photos and video with friends, but the people you share with can only view your files, not edit them. FileFly changes that with a Dropbox-like file-sharing service that allows you to share files with the Facebook friends that you select.
FileFly allows you to create folders and invite specific Facebook friends to access the folder and the files inside. Your friends will get notified, and they'll only be able to view or edit to the files you allow. The catch is that FileFly puts a 2GB storage cap on all files associated with your account.
If you already use Dropbox or any other file-syncing services, this won't replace any of those, but if you need to get a movie to a friend or relative who knows nothing of the internet outside of Facebook, FileFly can help.