It's a good idea, but you need to also consider the fact that you are limiting your chances of being surprised by people. Maybe someone in your "Health nut" circle is also secretly a geek, or maybe some guy in your geek circle shares your passion for politics. How would you ever find out if everyone always just posts stuff to people they think might be interested? This might very well be ok for you, depending on what you want to get out of G+.
What G+ needs is semantic filtering; some way for followers to filter out posts from individuals based on semantics. Let's say I were to post everything to Public (or to Circles, doesn't matter). My mom would certainly not be interested in my geeky posts, and with a semantic filter in place, she could automatically filter out the geeky posts of mine. I think I've seen somewhere that Google is working on something like this, and I very much welcom it.