This is a blog post. It has a definite topic, and it has a certain sender. However, it’s addressee is not yet determined. At least it was, until you chose to read it. As you went on to read these sentences, you assumed the role of the recipient, making this post reach you. Now, if you make a comment, this event of receiving will be clear for me and anyone else that passes by: you will be disclosed. If you do not, you will go on to occupy the default place of the undisclosed recipient.