If you cannot see tagged pictures of them,
the person that created the album and tagged your friend might have it private,
and you wont be able to see the pictures unless your friends with the original person who posted the album
my college roomates are not facebook friends with my highschool friends.
My college roomates have their albums set to "only friends" can see their pictures.
So if a college roomate tags my in a picture,
the number of pictures I have goes up,
by my high school friends cannot see the picture since they are not friends with the person who tagged me.