You can usually say you'd rather be interviewed than give a speech, and then they'll find someone to ask you questions you can answer, which tends to be much easier.

What I hope for in GoH speeches, and interviews, is awesome anecdotes that help explain how that person is who they are. Like Ken MacLeod talking about how the CIA financed his Trotskyist trip behind the Iron Curtain -- so secretly that he didn't know himself.