One of the things that drives me crazy is the speaker that says, "and, um" after every sentence or even more often. And, um... ya that drive me crazy. And, um...
Usually with a joke...or something about the way they were asked or who asked them to give the talk. But, normally just a funny first then the talk. I think it's just a way to get up there and get used to the mic, speaking, and shake the nerves off.