SAN FRANCISCO -- For years now, Silicon Valley has been searching in frustration for the next big breakthrough.
Innovative businesses that launched a decade ago, such as Uber and Airbnb, are finally making money or heading toward public offerings - but only after years of bruising fights with regulators and costly operational challenges.
At the same time, the dominance of Facebook, Google, Apple, and Amazon, has made it harder for new startups to burst on the scene. And the impact of powerful and much touted emerging tech, such as artificial intelligence and crypto-currencies, has been more incremental than explosive.
