OK, so there are quite a number of people with friends-only journals. Many of those also have one public entry that you can comment on, for example, if you want to be added, or want to contact the journal owner for some other reason.
What bemuses me is those who fall into the above category and who limit posting to their journal to "Friends" (i.e. disallow anonymous and non-friend comments). That would seem to negate the utility of such a public entry, no? At least, if comments are enabled on that entry at all... the only people who could comment could also see, and presumably comment on, the regular entries.
And if the journal owner doesn't list any contact details on their userinfo page, e.g. email or IM, then you can't get hold of them at all. Which is a valid choice, I suppose; I just find that (a) providing a public entry that seems to be for commenting on and then (b) stopping people from commenting on it seems a rather strange combination.