Some dev blogs have published information about the \"fb://\" url scheme for opening various views in the Facebook iPhone App. No matter how much I\'ve searched, I haven\'t
It's there to support the iOS push notification system (i.e. you get a push notification that says "Friend's Name tagged you in a photo", and you tap on it, it takes you straight to the photo).
I'd assume it's not intended for third party use and therefore subject to change. Hell, Facebook's public-facing APIs are subject to change on a whim anyhow, so I'd be especially cautious about something they hadn't documented.