Just What Is "the Passive Voice"?

Geoffrey K. Pullum, "Drinking the Strunkian Kool-Aid: victims of page 18":

Why are college-educated Americans so prone to think that simple active-voice intransitives like "bus blows up" or "took on racial overtones" or "were leaving" or "there will be setbacks" or "this happened," or even transitive examples like "has instructed us to," are in the passive voice?

(From Language Log.)