Is the golden age of startups over?

The tech sector is always buzzing with anticipation of the next hot startup and the next blockbuster IPO. These nimble, creative dynamos can appear out of nowhere with the power to create new demand for things we never knew we desperately needed. And experience has shown big companies that they need to stay alert to keep from getting knocked off the top of the heap by these newcomers. "For every lumbering Goliath," says Farhad Manjoo at The New York Times, it has long seemed that there...