DYLAN UPDATE: Rob Fagerlund reports that when he saw Bob Dylan play in Ann Arbor a few weeks ago, the concert began with the same bizarre introduction I described on Saturday. In fact, though he isn't completely sure, Rob thinks it may have been a member of the band who read it.
Brian Doherty, who saw Dylan three nights in a row this year in Los Angeles, informs me that the intro has been "the standard one on this tour, used as a self-deprecating joke." It was apparently derived, perhaps verbatim, from something a rock critic wrote about the singer last year. He adds: "It's a recording, of course, and I don't think the voice is anyone in the band -- just some pro announcer type. I might be wrong."
I'm glad to hear it's probably a deliberate joke. I never bought the theory that Dylan has lost his sense of humor, and am happy to see more evidence for my opinion.