I'll take a stab at this one. Atlanta is the "hub" of the South and a major city both in terms of business and tourism. It is also one of the busiest cities in the nation by way of through air traffic (Hartsfield-Jackson Airport). Also the division of Atlanta into many sects (Downtown, Mid-town, Perimeter Center, Buckhead, etc) means that business parks are scattered throughout the [rather large] expanse of the city. Since Starwood is a corporation that operates mainly business oriented hotels, it makes sense to have a number of properties in the greater ATL area.