Shape-changing interfaces are an emerging topic in HCI research: They merge the simplicity of tangible interfaces with the expressiveness of dynamic physical affordances. However, while prior work largely focused on technical aspects and proposed classifications of shape-changing interfaces based on the physical properties of the actuators and the user's levels of control, this work presents a classification of shape-changing interfaces based on the context and identity of the users. After introducing a new prototype for a shape-changing pushbutton, we conducted a series of workshop studies with designers and engineers to explore the design space and potential applications for this interface. We used the result of our workshops to propose a generalized taxonomy of interactions, and built two applications that reflect the proposed model. The paper concludes by highlighting future possible research directions for context and user aware shape-changing interfaces.