Your employer might not like your personal blog, as the latest instance of a personal blog affecting someone's life in a negative way can be seen in the story of Jessica Zenner. She was canned by Nintendo for posting things in her personal blog, which never actually mentioned Nintendo (and she wrote under a pen name). Still, Nintendo found it and gave her the boot.
Commenting on the situation, Nintendo's Perrin Kaplan says she "was expressly discouraged from doing what she did. I've seen everything that she's written and it's really not work appropriate." Of course, the situation has arguments for both sides, so we'll leave it up to you to claim who was in the wrong. Jessica or Nintendo?