Overall, I haven’t been too concerned about all this Facebook privacy alarmism that’s been going around recently, but this one took me by surprise. If you use the iPhone app to post a status update to Facebook (or use their mobile site), that update is visible to the entire world, regardless of your security settings:
I fired up the Facebook application for the iPhone. There’s a big “What’s on your mind” box that appears at the top. Enter something, like “I hate my boss,” and that message goes to your Wall — and to the world.
Unlike Facebook itself, there are no privacy settings that I can find in the application, no share with “Only Friends” choice. If you share via the iPhone — and perhaps other mobile devices — you share with the world. That’s also true if you use Facebook’s mobile site on the web. There’s no option there other than to share with the world.
So, status updates you do via the Facebook app are always visible to everyone and appear in searches. I’m not using Facebook on the iPhone for status updates any more.