I highly recommend David Roodman's recent reflections on the Kiva controversy he stirred up. Particularly unusual are the insights he reports from actually visiting the Kiva offices and talking to some of the folks there.
Development is at root about innovation and change. Innovation and change in turn have both a technology/policy dimension and a human/organizational dimension. We often focus on the technology/policy issues without enough attention to the human side, which can play an equal if not greater role in the success of a new approach. Our experience at GlobalGiving is that the ability of organizations to learn and respond is a key proxy for their effectiveness over time.
Roodman's description of how Kiva arrived where they did and what Kiva's management did about it after Roodman's initial post is an important story in itself.