Also, Paul Graham's premise, I'm sorry to say, is sensationalized (by invoking concepts like "inequality" and "startups") but wrong. The premise is, basically, "inequality has bad CAUSES, but startups and technology are never one of them."
Only at the end does he hint at what I believe to be the more accurate analysis: AUTOMATION and OUTSOURCING lowers demand for expensive human labor, therefore reducing one of the main ways that money trickles down to the middle and lower class. The better and more widespread the technology, the more I can
1) Outsource jobs to regions with a lower cost of living, leading to two losses of trickle-down:
1a) local workers don't get the job, and the money goes to someone in another country
1b) either way my company writes the expenses off its taxable income, but my country doesn't get the tax $$ from the worker's income to spend on social programs, safety nets etc.
This by itself is fine, unless you're a nationalist, because it helps reduce poverty where people are poorer, which is outside your country. However, technology also enables:
2) AUTOMATION, which means I now reduce the amount of HUMAN workers, and once again it has two aspects:
2a) Now, the demand for human labor drops, and since the supply of workers remains the same, their average wages drop.
2b) The worst one: monopolies with server farms, contracts of adhesion, and all the power. Like Amazon, Google, Apple, Microsoft, Facebook, Uber, etc. extracting rents from users and providers, until open source disrupts them.
By commoditizing the providers and workers, they get squeezed. See Amazon's dealings with wage slaves, and its tactics with publishers (middlemen which it eliminates). But those same workers are also supposed to be spending money back into the economy on things they need.
It takes time to invent new industries and educate everyone, there is no guarantee that will happen forever, and there is no guarantee that demand shocks for labor won't be severe. So, there should probably be unconditional basic income, negative tax or some other scheme for people to KEEP BEING ABLE TO AFFORD THE BASICS even if they face no prospects of making money, which a growing unemployed class will.
On the bright side, automation will help wean countries from their dependence on an ever-growing population to fund social security schemes. Endless population growth is unsustainable, and countries are currently worried about birth rates mainly because of that. So in a global sense, the solution is: tax the gains from automation, redistribute the proceeds, use condoms.