Privacy Policy is a Myth on Facebook

I have two major problems with Facebook's privacy policy: 1 - it doesn't work; and 2 - it's not a policy about privacy.  I don't know what the heck it's about really, so I'm thinking that maybe someone has to tell Mark Zuckerberg what "privacy" actually means.

"Privacy" is like Superman's fortress.  No one really knows where it is, except for a chosen few.  Wait, that's a bad example.  OK, let's go with the Batcave instead, because we can count on its secrecy better than Superman's fortress, which has been broken into by so many villains, including Lex Luthor.  Besides, I like Batman way more than Superman.  But going back to my point...

Have you ever noticed how Facebook's privacy settings don't really keep things private?  Just in case you don't know, there's something called "Privacy Settings" in Facebook.

BUT, it's got a gaping flaw: once you tag someone in any of your posts, anyone in that person's friends list can see the post -- including people who are not in your own friends list.  This is especially annoying when it comes to photos and videos.

I noticed this only recently when I posted a photo on my wall and tagged a few friends to it.  It later got a comment from someone I don't know and who's not on my friends list.  I traced him back to the friends list of a friend and realized that he commented on it after my friend tagged him to my photo.  That really took me for a spin: he was able to comment on a photo I had posted on my own Facebook wall, even if I've selected "Friends Only" as the people who can view and comment on my posts.

It's confusing for these reasons:
1 - Based on the concept of privacy and how privacy settings are implemented in other social networks, "tags" should be visible only among people you have "authorized" to view that information.
2 - Also, only "authorized" persons should be able to comment on my posts.
3 - Since I've restricted the access to all my posts only to people on my friends list, I expect people who are not in my friends list to not be able to see these posts -- even if they're in the friends list of the people I've tagged to my posts.
4 - What's up with the extra tag that my friend did on my post?  How and why was she able to do that?
5 - Why doesn't Facebook show an alert that says something like "You can't tag this person..." because of whatever, like "not authorized because not in the post owner's friends list".

What's the point of having filters if they can be compromised very easily?