sending a private message to your friends via Facebook IOS SDK

It is possible to send a private message via facebook- just not with the SDK. You can get the user's 'username' (ie. http://www.facebook.com/username) and you can send them an email via your app to '[email protected]'.

Shapow!

Major bonus: attach a file and it will be included in the facebook message.

One caveat: the email will not reach the recipient's message inbox unless the sender's email address is affiliated with a valid facebook user account. I would imagine this is in place to thwart spam.

No, it is not possible to send private messages using the Graph API.

Yes, it is still possible to post to a friend's wall. I just checked it out just now using the graph API Explorer tool: http://developers.facebook.com/tools/explorer. I used /friendId/feed with an HTTP post of "message" = "testing" and my friend confirmed they saw it on their stream.