Clifford Stoll, astronomer, scientist and author of Silicon Snake Oil, is undoubtedly a smart man (he once caught KGB hacker back in the infancy of the Internet). But did you know that he has a very ... unique form of public speaking? Great Scott!
Here's Clifford giving a talk at TED 2006 ... wait till he pulls out a slide rule! Hit play or go to Link [YouTube] - via Fazed
While he may take a while to get to a point, it's like reading a fractured narrative to me. There are lots of little points that seemingly do not add up or go anywhere, but if you can make the connections you can draw quite a bit from it, much as in this "lecture" where the shards are connected by the inscription on the bell.
There's no point in being highly memorable if what you're /teaching/ isn't remembered as well.