I have noticed that there seems to be 2 types of blogging -- blogging for information, such as Vicki Davis',
http://coolcatteacher.blogspot.com/2007/01/spies-like-us.html, or blogging to share or to communicate, such as Mrs. Edmison's class blog
http://blog.woodward.edu/ps_edmison/?p=281.
Blogging for information seems to be in the same genre as newspapers and the informational writing we teach our children. It helps teach things that we need to know or they think we need to know. It is written in a more formal voice than the other type of blogging that I have noted. In the educational world, this would be used more for professional purposes of the teacher and students than for entertainment or for recreational reading.
Blogging to share or to communicate would be compared to a friendly letter or, in more recent times, to email only blogging is in the public eye. The writing style is much more informal and easy to read. This would be the style that would easily move towards "conversations" with comments. This type of blogging is the type I began enjoying several years ago.
Blogging can definitely be educational. Students are able to share what they have learned, read what others have learned, or comment on what they have read (yeah for response to "literature"). Like I tell my students each year, we learn so much more about what we read when we think about it and then write about it -- whether it be asking questions about it, giving our opinion about it, or comparing it to something else we have read. Blogging is great for that!
On a personal note, I am not sure blogging is for me as a writer. As a person who can be pretty shy, blogging is very public and "out there". I have been working at this "thing" for the last 2 weeks and have had a very hard time sorting my feelings about blogs. This is something I will need to work on as the weeks go on.