1) Kiva spends to much money on marketing and is therefor inefficient. 2) Kiva gets to much media attention. 3) Kiva are attracting more than their share of micro-investors. 4) Kiva does not export Western cultural values.
Regarding number 4, I think individual investors should decided what and what not to fund. I find cock/dog-fighting to be inhumane, but I enjoy hunting, many people would say hunting is inhumane and immoral and a smaller group would go as far to say "eating meat is murder". What about businesses using malnourished horses to transport goods? Should Kiva not fund anything animal related?
As far as only funding legal organizations. I am sure Kiva does not fund narcotic production or gun running. But how can they possibly be sure all businesses they fund are 100% legal, complying with all health, zoning, retail, licensing etc. laws of the local county/state/country?