I think that's a factor as well. If the reader has a specific goal in mind, and your blog post presents itself as a way for the reader to satisfy their goal, then the reader will probably have less patience for stories.

But to take Spolsky's "Things You Should Never Do" as an example, obviously nobody's Googling, "things to never do," clicking Joel's article, and then getting annoyed at Joel for not telling them immediately. They're finding the post on HN, RSS readers, forums, etc., where they didn't have a specific goal in mind beyond learning/entertainment, so the author has more room to take their time.