A lot of your points are criticisms of blog posts, like "a lot of them don't have citations", or "a lot of them are poorly organized". These are true in many cases. However, if SIAI is considering whether to publish some given idea in paper or blog post form, they could simply spend the (fairly small) effort to write a blog post which was well organized and had citations, thereby making these problems moot.

... and if you're going through the effort of writing a blog post that's journal-quality anyway, you might as well go ahead and publish it as a full paper while you're at it.