Essays are the classic example that most people know by the time they finish school (I write optimistically). A paragraph begins with a topic sentence, contains the argument, and ends with a rewrite of the topic sentence to sum up what was just stated.
In fiction, paragraphing is based partly on topic and partly on character. The narration is determined not just by words, but by the punctuation - in which I include paragraphing. The beginning of a new paragraph indicates a greater pause, sometimes for change of topic, sometimes for a switch between description and speech, and sometimes just for emphasis.
Paragraphing in an article, however, is based more on the pattern of speech and emphasis than in an essay. An entire article is, effectively, a piece of dialogue. The paragraphs are short because very often people put all of their information into one sentence and then move on to the next important part, which with equal importance but different content, needs its own paragraph. And the sentences that serve to hit that point home, finally, always need to go on their own for their little whack of emphasis. I love emphasis.
This, however, is not an article. As much as I'm growing to like the spacing of an article - I quite hated it before I'd spent some time working with them, because I'm used to lovely, long fictitious paragraphs - it isn't appropriate here. In trying to determine what this is, exactly, I'd say it's something of a terribly written essay. I'm making a point, each of my separate ideas are in separate paragraphs, but I haven't even the class to do a proper topic sentence. Shows why it took me a while to do any good in writing them at school. Hopefully my Uni essays don't turn out as terribly as this one :/
(Perhaps structurally this is more like a feature article or column. That could be quite interesting.)