Instant messaging (IM) is a common and popular way for co-workers, friends, and family to stay in touch, but its "always-on" properties can sometimes lead people to feel overexposed or too readily available to others for conversation. This, in turn, may lead people to deceive others about their actual status or availability. In this paper, we introduce the notion of the "butler lie" to describe lies that allow for polite initiation and termination of conversations. We present results from a field study of 50 IM users, in which participants rated each of their messages at the time of sending to indicate whether or not it was deceptive. About one tenth of all IM messages were rated as lies and, of these, about one fifth were butler lies. These results suggest that butler lies are an important social practice in IM, and that existing approaches to interpersonal awareness, which focus on accurate assessment of availability, may need to take deception and other social practices into account.