I prob won't pay for reading blogs right now, as there is no single blog with content so compelling or desirable that I must read, that I will pay just to read it.
yvan, you seem to be describing wikis rather than blog, but I could be wrong.
But for that matter, wikis that are moderated by individuals or groups that are authoritative in the subject or field could be worth the money ... especially if alternate FOC options are lacking.
The other thing about blogs in my view that is different is its freeform style. Sure, many columnist are pretty freeform as well, but the fact that most columnists are doing it as their day-job tend to make me feel that their opinions may be handcuffed. For better or worse, blogs on the other hand, tend to make me feel that these are honest views or opinions of individuals or groups, who just want to have their say heard. Knowing that certain blogs are commercial kind of decrease the Keeping-It-Real factor.