Would it be appropriate to add a section to http://www.livejournal.com/support/faqbrowse.bml?faqid=219 [what is a friends page] about viewing other users' Friends lists? Possibly add in a mention of friendsfriends as a paid feature there, and note that the same public-post rules apply?
Edited to clarify: the mutual-friend and community viewing wouldn't apply to friendsfriends, but the security part would.
Edited again - it didn't occur to me to look in the troubleshooting category, and it's covered in http://www.livejournal.com/support/faqbrowse.bml?faqid=92 [Why don't journal entries show up where they should?].