Chatbots have been around for decades. However, the real buzz around this technology did not start until the spring of 2016. Reasons for the sudden renewed interest in chatbots include massive advances in artificial intelligence (AI) and a major usage shift from online social networks to mobile-messaging applications such as Facebook Messenger, Telegram, Slack, Kik, and Viber. The first of these reasons holds promise that intelligent chatbots may well be within reach. The second concerns service providers' need to reach users in the context of mobile messaging. However, in spite of these drivers, current chatbot applications suggest that conversational user interfaces still face substantial challenges, generally speaking, as well as for the field of human-computer interaction (HCI). Chatbots imply not only a change in the interface between users and technology; they also imply changing user dynamics and patterns of use.