I just got back from a week's vacation on Hawaii's Big Island and was surprised by the extensive cell phone coverage there. I expected that I'd find service only in larger towns such as Kona, but even in the more rural Captain Cook area, 45 minutes south of Kona, the T-Mobile and the Verizon networks were strong. I was especially surprised to find coverage at our guest house (highly recommended, by the way), which was a mile off the main road at 1,500 feet above sea level. Although T-Mobile petered out in Volcano National Park, Verizon continued to give us full bars. By contrast, in San Francisco, I can barely get service on some sections of Market Street. What's up with that?