That and the absence of "quality control" are the major problems I see. I don't know about our HW Helpers and Advisors, but I almost never venture into the Blogs. (I do, of course, if a blog posting is reported.)
My guess is that 99% of homework or other questions posted in blogs are just ignored or not even seen by someone who might be able to help. Lots of luck getting good help there.
Nonetheless, I think we should--at least for the record--make it clear that homework/textbook questions belong in the HW forums, not in blogs (or "Visitor Messages" or PMs, for that matter!).