This work extends the masspersonal communication model (MPCM; O'Sullivan & Carr, 2017) by introducing anticipated interaction as a way to understand variations within the masspersonal continuum. Drawing from Thompson's mediated communication framework (1995), we argue that anticipated interaction paves the way for establishing a communicative relationship between interactants. In social media, this relationship is rooted in a sender's expectations for audience response and the imagined responsive audience. Using experience sampling, we show that anticipated interaction varies across social media. Further, we outline the relational and situational factors associated with expecting response and the specificity of imagined responsive audience. These variations and their sources characterize masspersonal communication as a socially and technologically situated practice shaped by multiple intersecting influences.