Also, as an American transplanted in Vienna, I am very much not surprised to see that Austria leads the list with per-capita hackerspace density.
One of the interesting elements (that I suspect nobody here on Hacker News will mention) is government support.
As somebody else said, coworking kinda follows the gym membership model and hackerspaces are by nature more transitory, ephemeral, and more likely to "just go away" if people "wander off."
Austria, and the city of Vienna specifically, set aside a fairly significant budget for supporting local cultural projects and ones that advance Austria/Vienna in socio/economic/cultural ways.
Thus, for example, metalab has a primo location right by the Rathaus (city hall) that they could never afford if the city didn't support them. And Net Culture Lab is in the MuseumsQuartier, the very apex of hip govt-funded culture.