If the top poster has no banner and link configured, then a default banner will be displayed. We've made the add on like this, to encourage a credit exchange. What I mean by this is, if you for any reason don't want or need this setting, you can "sell" your advertisement space to another member. For example; I don't have the need to have a banner, so I can make a thread in the marketplace and allow another member to send me their link and banner to put in my setting for x amount time and x amount credits. If that makes sense.