This study examines the relevance of traditional mass communication's two-step flow-of-communication theory in relation to algorithmic personalization. I compare the two-step flow theory's concept of personalized content through opinion leaders with the current notion of personalized algorithms, arguing that opinion leaders and algorithms both function as gatekeeping agents. I also discuss the nature and role of peer groups in the two cases, arguing that while in the original theory, groups were seen as relatively solid (family, friends, and work colleagues), groups in the algorithmic era are much more liquid, transforming according to data inputs and users' behavior. Finally, the article also considers differences in the source of authority of opinion leaders and algorithms in both eras, as well as the different social settings and public awareness in the second step of the communication flow.
