The answer to this question may seem obvious to some, but let's see.
My impression is that some people write long blog posts about things that they perceive as innovative new ideas in philosophy, AI research, or whatever. So how do you decide that your idea should be a blogpost (here or on some other site) instead of submitting it to a journal?
Is the university research system just too closed? Or do you think it is superfluous?
Or do you think that you can do it faster for a blog? (This may not be unambiguously good. My impression is that there is less literature research for some blog articles than I would like to see, which often creates noise.)
Or do you want to have feedback for a blogpost first and submit later?
(Note that the question can be generalized to other media and forms, e.g. magazine essay vs. journal article.)