The elephant in the room: the death of the middle class.
Thirty years ago, unions were strong and average people had savings. Venture capitalists were wealthier than average, but not of a superior class... and they still hung out with people who wrote code for a living. Class distances weren't nonexistent, but they weren't nearly as sheer as they are today. And venture capital wasn't a requirement because bootstrapping was really possible, because average people actually had money.
People complain about how the Valley is cranking out apps for spoiled 20-year-olds instead of regular people, and missing the much bigger point, which is that "regular people" are cash-strapped, time-poor, overworked and generally disenfranchised altogether. The people building apps for spoiled 20-year-olds are staking out the new, post-large-middle-class world.
Now, to bankroll a business you either need elite connections (usually to people spending others' money) or outlandish luck, you have to have people in your pocket who'll ensure coverage, and you'll probably end up taking a back seat in your company as soon as you hire a "business co-founder" who can deliver Sequoia and A16Z.
No one has a good idea what to build, and products and technology aren't really the point (the point is getting bought; "startups" are a long audition process for would-be corporate executives looking to jump the queue) but one sector that isn't being targeted is the (disintegrating) middle class.
Corporate America, meanwhile, is stronger than ever. The wealth and connections are even more concentrated, giving power to the few at the expense of the many. And these Valley startups are the driving force behind all of this.