Originally Posted by kektex

Wordpress sucks at this.You have duplicate posts everywhere: on the archives, the category pages,tag pages,etc.
Again what happens here is that google just picks the version of the content that it thinks might be the original one on your site.
That happened to me on my first blog: all my domain.com/post/feed pages where getting indexed and the actual posts where nowhere to be found.
Learn to use robots.txt and NOINDEX