If you were about to seriously represent a small (say 6 meters wide) circular manmade structure in OSM, how would you do it? Several options:
 Point, because it is not large enough to be an area.
 Square, because at that scale shape detail is not so important, most people just need to know its location and approximate size. Maybe also because that’s what JOSM’s Simplify Way action does for features of very small size.
 Hexagon, because it is enough to tell the users it is not rectangular like most buildings. Implies 60° is the recommended minimum angular precision for most curves.
 Octagon, to avoid confusion with hexagonal features. Implies 45° is the recommended minimum angular precision for most curves.
 Dodecagon, because octagon is not enough. Implies 30° is the recommended minimum angular precision for most curves.
 Heptadecagon, because it is a known cultural threshold between regular polygons and circles. Implies 21° is the recommended minimum angular precision for most curves.
 Octadecagon, because it is above the heptadecagon threshold and even, so its edges align with rectangular features which may lie nearby. Implies 20° is the recommended minimum angular precision for most curves.
 Hexadecagon, because it is close to the heptadecagon and easier to subdivide than the octadecagon and also even. Implies 22.5° is the recommended minimum angular precision for most curves.
 Enneadecagon, because that’s what iD’s Create circle function does regardless of circle size. Implies 19° is the recommended minimum angular precision for most curves.
 More than 19 edges.
 Less than 19 edges, but other number.
And what would you answer if the curve represented a natural feature such as a coastline or the contour of a forest?
Some famous such objects already mapped and similar ones in the same country:

Pisa Tower: 16 m wide, 23 edges (16°)

hut in a park, Rome: 7 m wide, 8 edges (45°)

BT Tower, London: 13 m wide, 19 edges (19°)

nearby fountain: 7 m wide, 8 edges (45°)

Round Tower, Copenhagen: 17 m wide, 19 edges (19°)

nearby hut: 11 m wide, 9 edges (40°)

Fallturm, Bremen: 9 m wide, 18 edges (20°)

a small pavillion, Berlin: 8 m wide, 8 edges (45°)
More examples welcomed.
While crude geometry is undesirable, I also understand that there is such a thing as excessive detail (that which does not add interesting information), so there has to be something like an approximate ideal level of detail that balances the need for precise information and maintenance effort. Here are some links to support this view:
[/*] [*][Finland editing notes](https://wiki.openstreetmap.org/wiki/WikiProject_Finland#Editing_notes)[/*] [/list]