The real issue is that tech/startup founders and workers who, while less rich, accumulate more wealth at scale compare to the rest of society. And given their number, I'm afraid this will have a real impact by greatly increasing inequality. That would be ok if the other part of the population would also be able to live better. But I do not think it will be the case.
Btw: I am a tech founder.
This isn't just relegated to billionaires. Depending on how you define "consumption", up to 70% of the U.S. economy is consumer driven. Now I wouldn't call all this "unproductive" but it's probably selectively unfair to claim only the uber-rich are spending money on items they don't need.
Google, Microsoft, Twitter, Netflix, etc., are enormously valued and none of it is based on bounded resources.
People made rich by Google will absolutely be able to redirect more resources to themselves in a world of bounded resources.
I think a lot of founders are idealistic about it and refuse to believe that at scale the start up mentality will increase inequalities. That's PG's point acutally, see the last sentence of his essay: it will. But he doesn't care. I do.
That is why thinking purely in financial terms is misleading. It's not because everyone has more $$$ in the bank that everyone is better off.