Maybe blogs should have a little code or information block up front that tells readers what kind of blog they are.  Some suggestions:

Opinions - This is a personal blog, written by its owner, and will be interesting mainly to his friends and those who share his point of view and/or interests.

Public Interest - This is a blog about a subject of interest to the world-at-large (or some major part of it).  It may be written from a particular point of view (which should be clearly noted), but it is of interest to a broad audience.

Journalist Adjunct to a Publication - This is a blog that belongs to a publication (like a newspaper).  It is written according to the policies of the newspaper as a convenient way to provide additional coverage on a particular event or subject.

Journalist's Personal Blog - This is a blog that belongs to a journalist who writes for a publication but who uses his blog to express his views on other subjects in this place.  In that case, we will assume the newspaper (or other publication) doesn't edit or control the content of his blog unless he says otherwise.

Technical - Blogs about particular subjects, from computing to open heart surgery, generally of interest only to fellow practitioners.

Personal - Blogs used to share personal thoughts with friends or relatives.  Often private rather than public. Of interest onlly to the members of the group.

Social - Blogs used to communicate among the members of a group such as a club, team, study group, or other project.  May be private.  Of interest only to the members of the group.