Since I enabled the Login With Facebook feature on my iOS app, I am thinking about posting a feed to the user's wall indicating that the user is using my app. Technically I have solved the problem, but I want to double check with the experts here to make sure that's a mentally acceptable exercise. Please suggest.
Many users would certainly hate for their app to post to their wall directly without prompting, and will delete the app and tell everyone they knew to avoid it.
For that reason I advise to have a popup - "Hi New User, our app is more fun with friends. Let them know you use it too. Click here to post to wall." or even "This app would like to let your Facebook friends know you're using the app." "Post to wall", "Cancel".
You only have one chance to make a good impression and win over users.