Web storage and collaboration tool Dropio has just put out a useful new way to control who can access files by using Facebook Connect. Called "friend lock," the system uses your list of Facebook friends as a simple directory that you can pick and choose from to create a white list of approved contacts.
Once you've logged in with your Facebook credentials and pick the people who you want to be able to have access, you can fire off invites that show up in their Facebook in-boxes. You can also set it up to publish a note to your Facebook wall whenever you add or update a file within that storage drop (just like it can do with Twitter). Then, if one of your approved friends sees it, he or she can click on it in your news feed to hop right to it.
Here's a quick video of how it works:
This is one of the neater uses of Facebook Connect to come out thus far. Most services that have implemented it have simply used it as a way to let people skip registration and bounce data back to their news feeds. In this case, it's giving users a very high level of control over contact management outside of Facebook's walls.