I don't necessarily believe that all blog entries need to prove something. But I found some interesting discussions through a blog called "I Speak Of Dreams"> Liz writes about many, many subjects, but usually, she writes about education or learning disabilities. Almost every blog entry points out something I didn't know about or makes me think about something in a new way.
Evaluating sources is definitely an important skill when reading blogs. For example, let's say an annonymous commenter tells me that drinking "Potion X" will cure not only RSD, but blindness. The commenter leaves no backing studies and no links, except to their web site. As an aside, I probably wouldn't go to the site, depending on the comment, since I don't know for sure that it's not spam. I then need to evaluate that site, figure out where the commenter, and site, are getting their information. Is their information correct? Do they have actual facts to back their asertions up? Many of the questions asked in these three entries are helpful.
But I'm not sure that these questions always apply. For example, you can't necessarily always present the "other side". A personal entry doesn't always have more than one relevant side. Certainly there are times when that should be presented, such as when I get really mad, for example. But when you're dealing with the personal, the authenticity doesn't magically decline if I don't have five sources to back myself up.
In the last link I provided, the original author, David Warlick, states that
This [the first, original question] is certainly not limited to reading. The broader question is what preparations did you or the blogger you are reading make in writing this entry, or
what stimulus provoked the writing? This question seem useful on many levels, not just for academic assessment, but simply in being a responsible communicator in an increasingly networked digital world.
I definitely agree. It's hard to figure out where people are coming from even when talking face to face. "What provoked that?" Is a question I find myself asking certain people very frequently. As a blog reader, I sometimes wonder what made a blogger write something they did, or what made them write the way they did.
I'm not going to be rigid about any of these questions, but I'm certainly going to try to keep them in mind. Communication is one of the things I like the best about blogs.