I've worked in data centers for some of the largest financial institutions in the world, and I prefer to take a page out of there playbook.
They store the data in multiple locations -- period. The chances of catastrophe simultaneously in different parts of the country is incredibly small. You want the back up to be as far away from the source as possible. They don't squirrel it away on discs and bury it in the backyard.
Also, why presume that the servers for the online backup servers are overseas?? They don't need cheap sweatshop labor, and they aren't breaking US law which is the impetus behind placing servers overseas. It makes more sense for them to keep it domestic -- i'm not sure myself but i'm going to find out for sure.