News flash: Cities aren't what they used to be. Follow-up question: What is? This rather obvious query popped into my head Sunday after reading Joel Kotkin's sniffish dismissal of San Francisco as an "ephemeral city," one that "differs dramatically from traditional urban centers." Instead of smokestacks and stevedores we have tapas and trust-fund liberals. He's absolutely right, and he totally misses the point. If San Francisco is a far cry from the boisterous Big Cities of yore, that's because Big Cities continue to evolve. The successful ones still draw strength from immigration and a central address, but they're no longer...