Second things first: Google Plus is too all-encompassing and controlling. I can’t get a feed to publish elsewhere, or hack at, or stream, or store as text. Anything I write there lives ONLY in Google Plus, it seems, and can be taken out only manually.
And I’m not sure I want to write primarily for my friends. If I wanted to tell my friends something, I’d send them an email. If I have an idea to share, it seems cleaner in some way to publish it anonymously – or at least without notifying my friends – so that it stands on its own merits, and the reaction to it is not muddled up with relationships and niceness. Besides, if the writing is both honest and personal, it may relate to people my friends know or would recognize, and that is the last thing I would want. Unavoidable, perhaps, but not desireable.
Postscript: Google Plus may open itself up when the API is launched: http://www.readwriteweb.com/hack/2011/06/google-plus-puts-out-a-call-for-developers.php