How is this for an excuse for speaking non-sense; researches says that you can't speak and think at the same time.
Shneiderman says researchers in his computer science lab discovered through controlled experiments that when you tell your computer to "page down" or "italicize that word" by speaking aloud, you're gobbling up precious chunks of memory -- leaving you with little brainpower to focus on the task at hand. It's easier to type or click a mouse while thinking about something else because hand-eye coordination uses a different part of the brain, the researchers concluded.
Yes yes, I do realize that holding a conversation is a different process than giving commands to a computer; but then that kinda ruins the joke.
(via ars technica)