<SF could double it's current housing density tomorrow and still have less than half of manhatten's density. That's not a serious concern.> Count how many brid

<SF could double it's current housing density tomorrow and still have less than half of manhatten's density. That's not a serious concern.> Count how many bridges and tubes connect Manhattan to the mainland vs. how many bridges and freeways connect SF to the rest of the world, and revisit that concept again.