A common slipstream

Life is full of slipstreams. You know, you and a friend chatting away on a subject of interest and another friend comes and sits down with you. Right in the middle of your brilliant delivery of most profound thought, he/she butts in and the subject matter instantly changes. You have just been slipstreamed! This common slipstream event is practiced daily by the majority of people living in the world today. Go on, you know you do it, too!