I am the developer. As noted on the page: Unlike GeoNames, look-ups are based on an actual map of the world, rather than "closest point of interest", which ensu

I am the developer. As noted on the page: Unlike GeoNames, look-ups are based on an actual map of the world, rather than "closest point of interest", which ensures accuracy and that you actually get a result for all locations. We also have a very fast spatial index rather than a slow SQL-GIS solution, and last time I checked, they have usage volume restrictions that are pretty limiting. We looked into using them before building our own solution.