Consumers' active and discretionary use of social media is influenced by a myriad of individual attributes. Which of these attributes really matter and how do they matter? This article proposes an exploratory structural-equation model comprising five constructs (“Big Five” personality dimensions, motives, involvement, content preferences, and usage) derived from the cognitive-affective personality system theory and 3M model of motivation and personality. Applied to a survey of 656 YouTube users, the findings indicated that participation in social media can be understood parsimoniously as oriented toward the self (individualist) or others (relational). The psychological profiles obtained suggest that relational-oriented consumers make a better target group when seeding a campaign than early adopters, as the former are more likely to generate word-of-mouth, and can be targeted by messages emphasizing informational learning.