There's no restriction for what a podcast should and should not be. Of course, if you cover all these topics and more, you may find it harder to find an audience than if you focus on a narrower range and cover it well. Finding listeners is simpler if your podcast can be summarized in a sentence. More people will sample your show if it fits in a category in a podcast directory—like that found in the iTunes Store—than if it ends up lumped in a generic catch-all list.