That makes sense. But what can I do if the screen name is left blank? I have then many users posting with an empty author field.
I have to offer the forum admin the choice to create an anonymous forum. So what shall I do to have unique aliases in the forum but not empty ones. I could go over the users table and automatically create screen names as a combination of first_names and a counter. What do you think of that? If a user wants to change his screen name he has to find then a unique one later on.
