When we built our first batch of toilets in a village, we thought that we could save some money by building only a few of them and that villagers would share them. After all, they don't ALL go at the same time, do they, so it seemed to make sense.
Rapidly we saw that these toilets were not used at all. We thought it was a matter of education so a team of people set out to demonstrate (yes, demonstrate) how to use them. Picture the scene : a bunch of villagers gathered around a toilet, with a guy inside showing how to do... What a laugh, but still nothing. We asked around. Nobody knew. So we made a public offer : we would pay the people to use the toilets. One rupee a wee-wee ! This time, we thought, these damn villagers are going to do it. For the money, if nothing else.
Nothing happened. We felt miserable.
Finally somebody realized the problem : there were people from different castes in the village and they wouldn't share their toilets with somebody of an other castes. Period. So we resolved to build one toilet per house and it worked like a charm....
This shows that no matter how good your intentions, you can be totally wrong if you don't understand the motives of who you're talking to. This has been an incredibly useful lesson to us since.
