Yup, it's less obviously progress for people whose rents spike up, because that is objectively bad, as I said. But long term it's better to have people moving back into urban centers than the massive outflow we had in the 1960s, which did not create a utopia for the largely poor and minority residents who remained, in fact crime and joblessness skyrocketed.

It's complicated and there is suckage all around, as I tried to acknowledge, but having tech companies clustered in the urban core is better on many levels than having them dispersed out into suburbs or the midwest or whatever the OP was envisioning. Was Mid Market REALLY better off with just strip clubs, liquor stores, greasy spoons, and scattered social service agencies than it is with some of those things plus Twitter, a VC firm, and some other tech startups? Really?

I don't think the only two options are Detroit and Manhattan.

Also, I think the mid-Market area is perhaps not the only place we can look at in evaluating the effects on San Francisco.

At least we're agreed it's not part of an "ugly urban cycle."

We agree that it's not ugly if you've got plenty of money. If you're one of the people forced out, then it is little consolation that the richer people who replace you think the city is "better off".

I'd be really interested to see the argument in which the city is better off in the opposite case - the startups all, as OP suggested, keep to the suburbs (like Pleasanton) or cheaper Midwestern cities (won't the gentrification just move to those cities?) or maybe the middle of nowhere where no one will be gentrified but everyone has to spew loads of CO2 into the atmosphere to get there.

Has anybody sane proposed that we pursue the opposite case?

Welcome to Earth. This is a world and existence of limited resources.

That doesn't mean your way of allocating them is optimal.

There are many ways of allocating resources. A free market (if and when it exists) is one, and it tends to be efficient, if not fair.

Others include lottery, kleptocracy, autocracy, social-welfare state, theocracy, anarchy, communism, socialism, despotism.

"There is no god but the Market, and Milton Friedman is his Prophet!"

In the name of the Dollar, and of Saint Ayn, and of the the Trickle Down: amen, amen.