If you have a wordpress blog, you must have noticed in your admin settings page that you cannot change your login name once it is set. So, you believe that once you get some stereotypical name like Admin(default) you cannot change it later like you MSN or Gmail username. In case of single author blogs, people generally leave the username to default i.e. admin, which everyone can pretty much guess on. Even if you have a multi-author blog, you might need to change the username for other contributing writers for some reasons. You cannot do it via the Admin interface but can do it very easily from PhpMyAdmin.