In the Web UI, it can be tiresome to add "Friends", "Family", "Acquaintances" or "Public" or whatever. It might be nice to have a way to specify your addressing defaults.
Certainly there should be a way to say "Make all of my posts public." or "By default public." What is done with other lists might be related, but other lists aside, the public option is most assuredly going to be in demand. It already was, of course ... identi.ca users were, by and large, posting publicly.