The article is concerned with teaching language by utilizing social media from a social justice perspective. It makes an argument for taking a dialogic approach to pedagogy based on serendipity and contingent scaffolding. The article is inspired by a small but growing body of literature known as Critical Computer-Assisted Language Learning. First, I provide a brief introduction to Computer-Assisted Language Learning, and its recent turn toward a critical approach. Then, I discuss social media, and what "social" means when it precedes the word "media." Next, I describe how social media are being used in language education, and why the dominant methods of use may not prepare language learners as justice-oriented democratic citizens. A key barrier I identify in this regard is media users' increasing ability to filter what they want to see and hear. To re-think the pedagogical uses of social media, I draw from Mikhail Bakhtin's works and propose a dialogic approach, which may be helpful for language teachers and teacher educators.