How likely is it that someone might abuse the app and graffiti our Church wall?

This is highly unlikely.  Posting to your church wall with malicious intent is an extremely rare occurrence and as the writing of this post (10/10/15), it has never happened on SmartChurch to our knowledge. Remember, this Follower can be removed if they are flagged for inappropriate posts three or more times in Freemium or removed instantly if your church uses Premium.