If I don't flock it, then the world is free to see it. And if it gets linked from another journal, all the better - if it's unlocked then I want people to read it. That's why I blog, right? For other people to read?

And if I don't want it publicly accessible, I flock. And if I don't want everyone on my flist to read it, I filter.

Very occasionally, a public post will become a private post if it attracts the wrong kind of attention but that's very rare. But I never complain if new people find my stuff.