If the company has 10 locations throughout the world and the Data Center in USA. You design OSPF in a way that USA routers are in Area 0 and branches throughout the world in Area 1 for the Branch in Germany, Area 2 for the branch in France and so on. If someone in Germany has to communicate with a user France then the packets must come to USA and transit through OSPF Area 0. Is this an optimal design that requires packet to come all the way to USA then back to Europe.
I guess what I am saying since all areas are required to go through backbone area 0 but how to avoid the situation I described above.