So +Mike Elgan
What you are also omitting is that you will
1- address it to Public (and your public/blog circle) for a blog post,
2- address it to a specific circle (and your Tweets Circle) for tweet-like,
3- address it to customer (and the "specific company circle") for business
4- a single person for personal letters.
This way you keep track of what you send in which context and can find it faster. I wonder if I can put myself in those "special" circles or simply keep them empty.