The primary thing to remember about LiveJournal's FOAF information is that it's not presenting new or different information, only a new format. All the information available in my FOAF file is equally available in my User Information: compare http://crschmidt.livejournal.com/info to http://crschmidt.livejournal.com/data/foaf .
If you don't want your contact information shared, there's an easy solution - simply choose to not have your information shown to all users, which will block it from your FOAF file as well. If you would like to block your FOAF file from containing information like your friendships, you can do so by including a URL in the Edit Information page, at http://www.livejournal.com/editinfo.bml - simply fill in the "External FOAF URL" field.
LiveJournal allows options to block a certain subset of information, which FOAF respects. Any information that is displayed is not information that's difficult to find - simply parse the user information page.
That's why LiveJournal FOAF really isn't a big deal from a privacy standpoint: the information is already there.