Since the release of the timeline profile, a declining trend in the number of spamming wallposts in one’s profile page is observed.
Facebook has moved further by having a plan to remove the ability to post to a user’s friends’ walls via the Graph API.
See if you apps are being affected by this proposed change. If your apps are being affected, then it is recommended to invoke the feed dialog so that user can publish the wallpost to his friends’ walls interactively instead of having your apps to perform the wallpost publishing via Graph API. Besides, Facebook has mentioned that stories that include friends via user mentions tagging or action tagging will show up on the friend’s timeline (assuming the friend approves the tag). So, may be you can consider that as an option too.