Hi smithm9, I also do not know of any study that definitively "proves" that microfinance alleviates poverty. I think one reason is that it is hard to decouple the effects of microfinance from the many random events that determine household income in developing countries. Another reason is the high interest rates charged by most traditional microfinance programs.
I have personally known many people who have dramatically improved their living standards thanks to Zidisha loans. Here is one example: https://www.zidisha.org/microfinance/loan/nbsarr/408.html (see the comment area for updates on the results of her loans).
Over and beyond measurable economic effects, I would argue that having access to the chance to raise affordable financing is transformative because it changes the way a person views the range of opportunities for advancement in life. For example, all Zidisha entrepreneurs know they can progress to raise up to $10,000 if they maintain a solid track record of repayments over time. Simply knowing that opportunity exists removes the ceiling people would otherwise put on their own ambitions. The result is intangible, but no less important because we cannot measure it.
We structured Zidisha as a nonprofit because our mission is genuinely philanthropic. Nobody is in it to make money. At heart, we are a cause-driven group of people and the nonprofit structure is a natural fit for that. Also, we do not want to be in a position where equity holders might oblige us to charge high fees to generate profits. Finally, our nonprofit status reinforces the message that lending through Zidisha is a philanthropic, not a financial investment activity.
Why do we accept donations to run our organization? We provide a valuable service to lenders in developing and maintaining the web platform and community that allows them to connect with the entrepreneurs they wish to support. We could charge lenders a fixed fee to cover the cost of this service, but we decided to structure it instead as an optional tip made while funding loans. The optional tip allows lenders who can afford more to donate generously.
Currently about half of our income comes from service fees paid by borrowers, and the rest comes from lender tips. We view both as payment for service we are providing, rather than a free handout.