“By 1972, E.B. White had picked up the idea and added a flailing, incoherent, angry, foaming-at-the-mouth paragraph to the 2nd (1972) edition of his revision of The Elements of Style. He calls the sentence-introducing hopefully silly, unclear, free-floating, offensive, ambiguous, soft, nonsense – in other words, he has no idea what he wants to say about it. He just hates it so much that he wants to spit.
Geoffrey Pullum, in The Truth About English Grammar