lets block all search traffic and then take this even further -- lets have all incoming links get forwarded to a dummy hacker news with nothing but lame stuff so that anyone trying to access the site from a blog or something with an HTTP_REFERER will get redirected to the lame site. that'll definitely keep out the unwashed masses. :)
Even better: replace HN with a static snapshot of it as it exists right now! Then we know it will always be this good! :-D
although that would probably turn out badly