Niti Bhan wrote a long article on Core77 on marketing to the Bottom of the Pyramid.
“The premise of the fortune at the base of the pyramid (BoP) is based on the notion of how to profitably do business with the poor. But few such endeavours have become sustainable businesses, falling prey to bad assumptions, misguided marketing, or poor research.” [...]
“Using the 5D’s—development, design, distribution, demand and dignity—can provide a roadmap for a cohesive, human-centered strategy for well-designed products that sell, services that are successful, and programs with low drop-out rates. Observation and user research conducted to understand your new target audience is critical in establishing the relevant value propositions.”