I'll butt in here re the UN with a 'ground level ' point of view.
My wife never left Cambodia til she was 23. She lived in Battambang province. She and her mother survived the Khmer Rouge (lost her father and sister). Her attitude towards the UN was that there is widespeed corruption, its a very matter of fact attitude, ie not judgemental, just "oh yeah, they took bribes to look the other way. Some of the UN guys would pay good money for a young virgin" - stuff like that. Considering the corruption in Cambodia most people there regard that as normal behaviour.
The UN is like any other frontline organisation, it has good and bad people. If you think that UN inspectors wouldn't/don't take bribes then you lead a very sheltered life.