Pretty accurate, at least for the 15 or so surnames I searched. All branches of my family, except one, come from Spain. I rearched most of the surnames and was able to get information on many (Basque, Castillian, Cantabric) and those roots are still reflected on this map. By that I mean they are most dense where they originated (some even 700 years ago), indepedent if they're toponymic or not.