Facebook’s initial public offering later this spring will create a billion-dollar windfall for its founders and early investors, so it’s easy to be cynical and view the IPO as another example of insiders cashing in on the latest web phenomenon. But the significance — and symbolism  — of Facebook’s IPO goes much deeper. Facebook’s astonishing rise is an apt metaphor for the emergence over the last two decades of the Internet itself as a tool for individual self-expression and collective organization. It’s also a dramatic example of a generational shift taking place among the entrepreneurial class, one that elevates social change as a priority along with commercial success. Perhaps most importantly, Facebook’s success is a powerful argument to the...