“…This may ultimately result in better theories about how advertising on social media works. At the moment, however, theory building is problematic because almost all existing studies of social media advertising (for an excellent review, see Knoll 2016) focus on social media in general (e.g., Muntinga, Moorman, and Smit 2011;Okazaki, Rubio, and Campo 2014;Van Noort, Antheunis, and Verlegh 2014) or on one specific social media platform, such as Facebook (e.g., Chi 2011;Chu 2011;Nelson-Field, Riebe, and Sharp 2012), YouTube (Liu-Thompkins 2012;Walther et al 2010), Twitter (Liu, Burns, and Hou 2017;Sook Kwon et al 2014), or Pinterest (Phillips, Miller, and McQuarrie 2014). Social media, so it seems, is regarded as either an umbrella concept or a specific social medium seen as exemplary for all social media.…”