Smart mobile services and applications use users' context. However, we never investigate how users perceive this context and how to leverage this perception for even smarter services. We represent the perception of the context of users as their intimacy, their familiarity with their current place, the number, and kind of people around them. The adjective ‘intimate' describes the context as familiar, being private and comfortable. First, we validate the intimacy concept. We establish that users use mobile services differently in different intimacy situations, and we create a first theoretical model to estimate their intimacy. Second, we investigate the intimacy predictability in practice (limitations and solutions). Finally, we show how we can leverage intimacy for studies on users' context or deploy our intimacy model to help apps developer. Advertisers can use it to deliver their content, and it can support the innovative projects, as Google Project Tango, to get smarter.