Sean Stannard Stockton, who writes the blog Tactical Philanthropy commented Kiva.org's problem finding enough people to borrow all the money that people want to give. He rightly points out that there are probably many people who would like to borrow, but aren't able to for lack of microfinance access – leaving Kiva and its partners with the challenge of building that access. This supply-demand balancing act is to be expected.
I’d like to add that this may be another case in which philanthropists should be more open to what they are willing to support. It may be more emotionally rewarding to give money directly to a microentrepreneur in Chile than the NGO that transfers the money, but it may not be as effective in the long run. Microfinance institutions can't expand their client lists without resources.
