Well, right off the bat I can tell you they don't have all of the lairs on there; the Yucatan and Seattle both have guaranteed dragon lairs which aren't marked. On top of that, while the Greats and a few others are known, there's a lot of dragons who don't hit the big leagues/books.
I'd consider any marked lairs on that map without a linked dragon to be a plot-hook; a GM looks at the map, sees a lair without a dragon and goes 'Gee, what could I do with a lair in the ass-end of nowhere?' Detroit and Charlottetown are the two I couldn't hazard a guess as to who owns them. 7 lairs for 9.5 million square miles? Dragons are more common than that; it's even stated that many have multiple lairs. Celedyr, Hestaby, Sirrurg, Ghostwalker and the Dragon Formerly Known as Dunkelzhan are all Great Dragons based in North America, not including the lairs other Greats have for travel. Then there's Dzitbalchen (deceased), Perianwyr, Damon, Eliohann, Haesslich, Pobre, Sonador, Zuacaltipan, Henequen... There's more dragons than lairs, that's for sure. And those are all the dragons I could find with a few minutes of research/trawling my memory.
