As those who were in San Francisco in the mid-nineties know, there is no place so exciting as ground zero of an explosion in intellectual capital. Africa, with a population of 1 billion people, 50 percent of whom are under 30, connected as never before to the global community and with tools to build with that many more people can afford, is in the midst of a renaissance that could make the Bay Area’s last-century heyday seem like a footnote.