Smartphones are more prevalent than computers in the digital age, particularly in poor and minority communities. Is it the effect to reduce or perpetuate socioeconomic disparities? This article reviews two decades of research investigating whether mobile phones contribute to enhancing the status of disadvantaged populations. Conclusions on the nature and extent of the mobile effect vary across areas of inquiry, including digital inequality, social networks, and coordination and mobility. Advantages accrue in particular areas, such as strengthening core ties, promoting particular Internet activities, and enhancing daily coordination and safety. Device limitations and structural inequalities overwhelm the mobile effect in many arenas, though new conditions emerge with changes in mobile technology and digital habits. Future research will benefit from closer attention to how mobile affordances, user motivation and habituation, popular mobile uses, and the particular conditions of disadvantage shape outcomes for marginalized populations.