While social commerce research has predominantly focused on how established brands attract consumers, very little is known about what motivates individuals to risk purchasing from shops owned by other individuals. The study investigates the underlying factors influencing Indonesian consumers’ intentions to purchase lifestyle goods on Instagram shops, despite the lack of financial safeguards against fraudulence. Extending the theory of motivated reasoning, the findings show that perceived constraints to purchase through other channels moderate the effects of key variables that influence trust and purchase intentions. Perceived ease and security of transactions on social media shops only correlate with trust for consumers who perceive they have unrestricted control over where to purchase. However, these relationships were not significant for consumers who perceive high constraints over alternate purchase channels. The findings extend the understanding on the boundary conditions of social media marketing, particularly in emerging economies.