Yes, I think the privacy advocates use the 4th and 9th amendments as Constitutional justification for protecting privacy, the 9th being especially cryptic and non-specific (and the one amendment that nobody really knows or cares about): "The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people." What the hell are "others retained by the people"? I suppose they're whatever we agree they are. I would argue that privacy is a valuable right that shouldn't be denied us if possible. To me, the 9th (and of course, I'm no scholar on this matter, either, just an interested citizen) basically says that we can't construct any law, or condone any behavior, that abridges any fundamental human right, even if that right isn't specifically mentioned in the first eight amendments.
It's always hard to find clear and concise literature on these sorts of things but my gut feeling (haha) is that the ninth amendment doesn't have an extensive jurisprudence or case history because it's so vague. No judge could cross through that thicket without being accused of making some shit up (even though that hasn't necessarily stopped Justices before).