May I ask what is the aim of fill in an email address when one wants to leave a comment. For example, in this page: http://ux.stackexchange.com/questions/6959/c

May I ask what is the aim of fill in an email address when one wants to leave a comment. For example, in this page: http://ux.stackexchange.com/questions/6959/contact-form-or-mailto-link http://ux.stackexchange.com/questions/6959/contact-form-or-m..., at the bottom, you can post as a guest, but the email address is necessary.