See https://lists.openstreetmap.org/pipermail/tagging/2015-March/022375.html

With openpoimap it is even more striking! Openpoimap is a great tool to discover (and sometimes fix) this kind of data. I start developping it a few months ago and it has an increasing number of users. Especially useful to check if data you have entered on the map is correct.

I doubt if the things tagged as toilets in Tandale are private toilets, some are probably Open Defecation Areas, others might be communal toilets. Most of the 50k+ inhabitants will not have access to any kind of private toilet facility. An overpass query counts around 550 POIs, so roughly 100 people:1 toilet.

Tandale has been mapped by local people with guidance from experienced OpenStreetMappers.under a Development Seed programme.

I suggest reading some of the following:

• Community Mapping in Tandale
• Gary Gale’s Visit
• Ground Truth blog

And a youtube video of Mark Iliffe and Gary Gale made in Tandale.