The advantages are more numerous than the disadvantages. For example, they can fill a big vacuum that many governments around the world cannot do. They can also transverse boundaries and borders (of course, with local government consent) between countries that often do not get along and or recognize each other. Because they are seen as humanitarian and beneficial to the local people. They usually rely on private donations/funding to do their work, not government money. Disadvantages include danger working in those zones/areas - wars, extreme poverty, looters, costly and time consuming to do the job, and dependence on the goodwill of the countries to allow them to do the work. Their staff earns little and most are voluntary workers.