My own pedagogical term for this is “richly-linked blog post” — emphasizing the value of hyperlinking to sources, evidence, definitions, counterpoints, etc. (Thanks for the link, John S.)
Sorry, I don’t have a better name for it, but I feel it needs a succinct name so we can identify and discuss it. It’s not a tossed-off short blog post. It’s not a long, involved essay. It’s somewhere in between: it’s a blessay.
The blessay is a manifestation of the convergence of journalism and scholarship in mid-length forms online. (For those keeping track at home, #7 on my list of ways that journalism and the humanities are merging in digital media). You’ve seen it on The Atlantic‘s website, on smart blogs like BLDGBLOG and Snarkmarket, and on sites that aggregate high-quality longform web writing.