Blogs are parallel to research papers in a sense. They're useless without peer review unless you're already intimately familiar with the source material and able to critically evaluate the contents.
So Blogs are more useful when they're aggregated through a site like Reddit, where users have already done the vetting on whether the linked page is valuable. Reddit comments are invaluable to pages by adding additional context. Noting when the content has become dated or inaccurate due to external changes, etc. Sites like Brian Kreb's blog are the exception as the author is well known and respected. But the general blogs? It takes time to earn that community respect.
Then beyond that, how often have you gone on the hunt for something obscure only to run across 3 or more blog pages which look entirely unique, but have the exact same article pasted to them? It isn't that the contents are bad/wrong/inaccurate, but rather who do you trust? How much effort are you going to put in to finding which blog was the original, written by the expert and which ones are bots copying the info?