Your Application Settings in Facebook may be restricting what permission level dlvr.it is able to post using. (We may be saying Public, but Facebook is overriding it.)

Visit the Application Settings page in Facebook: https://www.facebook.com/settings?tab=applications

Edit dlvr.it's settings, and ensure that "App activity privacy:" is set to Public. This setting defines the *maximum* level that an application is able to post using. So, when set to Public, it allows us to use Public, Friends, etc. If set to Friends, then it only allows for Friends or below, etc.