(The following was originally posted to Facebook yesterday, but given the subject of my previous post on how I use social networks, I thought it would be appropriate to include my thoughts here as well.)

The auto-sharing feature that I discovered today has me thinking about how privacy works in Facebook.

Facebook doesn’t protect your privacy as much as it sets up sharing contexts based on the connections people establish. Once you post something to facebook, there is nothing preventing it from being shared with everyone on facebook. The only privacy control that you have is that the post isn’t shared automatically with everyone but has to propagate between social graphs, and that propagation can only be initiated by people. I would guess that most posts are not shared forward, meaning that they stay within whatever sharing context you initially intended the post to have. If someone has a reason for sharing your post with their social graph, they can and there is nothing you can do to prevent them from doing so.

This is what passes for privacy on Facebook, and it does to a large extent mirror “real life”. If I tell 500 people that I had an artichoke and cheese sandwich for lunch, there is a good chance that they are not really going to pass that information on to anyone, mostly because they would (correctly) assume that other people wouldn’t be interested. If I tell 500 people that I’m away on vacation for two weeks and share a picture of the beach I’m sitting on, well, maybe a few might share that information with their social network, and I probably don’t care if most of those people do, but maybe there are a few where I do care, and what business did X have in sharing that with them? And why did I share that with X in the first place?

The answer to both of these questions is rooted in the fact that both X and I misunderstand what our social graphs of “friends” truely represent, that within this group of friends there are actually several circles of trust, ranging from our closest friends that we trust alot to acquaintences that we trust little more than strangers.

Yes, Facebook does provide the ability for us to create lists to represent these various circles of trust, but setting them up, maintaining them, and choosing which to use is extra work. Still, I think it is worth spending some time investigating these options so that I can refine my use of Facebook so that I can continue to use it to interact with people I know without worrying about where the information I share is going to end up!