The sentence we don’t like about the FAQuestion on deletion is: “However, you will need to manually delete any comments or entries you posted in other journals/communities.” That may be a lot of work!
This means a completely automated deletion is impossible. Anyway… Be logged in, use the link to delete and deactivate your journal (account). You have 30 days to undelete your account. Also read http://www.livejournal.com/support/faqbrowse.bml?faqid=16