Do blogs really need to be theme-specific?

If so, I guess I'll need to choose a focus. My choices are:

1. Career woman in transit/crisis (Big world-gulping company, small, do-good nonprofit, business for myself, what do I want to do when I grow up?)
2. Wife and mother in transit/crisis (In two years we'll be empty-nesters. Am I ready? Will we be OK as husband and wife alone in a big empty house after 20-some years of four lively kids sucking -- and giving -- energy?)
3. My somewhat irrational drive to get back to Germany. ("Back?" It was my parents who lived there, not me. I have only visited. And granted, I almost married a German -- still my dear friend, and yeah, I do miss him sometimes -- but I never WAS a German. So why do I say "back" to Germany?!)
4. Picture posts. I love blogs with pictures! And goodness knows, I'm obsessed with my camera!