The use of ephemeral media platforms, like Instagram Stories, has been growing and the ephemeral characteristic of these platforms has created a new form of interaction mediated by technology. This work aimed to characterize how Instagram Stories supports the sociability among its members and to discuss the impact of this proposed sociability in the social interaction of users. We conducted this research in three steps. First, we executed an evaluation in a perspective of Human-Computer Interaction (HCI) experts, which aimed to analyze whether the features offered by Instagram Stories are adequate to user experience (UX) and sociability guidelines. Next, we performed an evaluation from the users' perspective, in order to investigate users' experience while they are interacting through Instagram Stories. Finally, we made a triangulation of the results and we discussed the impact of Instagram Stories in the social interaction of users. The results showed that the interface and interaction model of Instagram Stories reflects directly on the experience of use and sociability of its members, once this system offers features to support the social interaction, but the way these features are available on interface may limit the sociability among its users. As contributions, this work reinforces the importance of sociability as a strategy of use quality to improve user experience and social interaction on collaborative systems. Besides that, we present recommendations and insights to Collaborative Systems and HCI communities about the design and evaluation of ephemeral communication services.