What do you think should happen to you if your house is more valuable in a year than the year before, even if you aren't selling or otherwise leaving that house?

This varies wildly depending state you live in - some states adjust property taxes for current value, some don’t (or do but with severe limits)

But do they do income-like taxes on the added value? This seems to be what people (GGP) are wanting from the increase in stock values, ie, unrealized capital gains.. which is frankly terrifying.

They increase property taxes, so yeah, you're getting taxed on a capital gain that you haven't realized yet (and won't until you...sell your house).

What do you think should happen to people's retirement accounts each year then?

Nothing. Retirement accounts are tax deferred or tax free. What a weird question to ask.

Well, if you want to tax the stocks that the wealthy own.. why wouldn't you want to tax the stocks that many regular people own? Where do you draw the line between the two?

Wealthy people's stock in retirement accounts would also not be taxed. This can be considerable: Peter Thiel's Facebook investment was made in an IRA.

I imagine there'd be some net worth number, excluding retirement accounts, that policy wonks could work up. You draw the line between "wealthy" and "regular" there. Or, more likely, several lines because there would be wealth brackets similar to income brackets. Without that it would be a regressive tax.

Why not just tax when someone SELLS the stock, or leverages it for a loan instead? You know, when they actually use it?

I'm actually against property taxes, or any kind of tax where you risk losing property just because you managed to live another year.

I don't disagree with that. But it's a much bigger discussion. Abolishing all property taxes means city and county finances need fundamental re-working.

I know what does happen. Property taxes go up. A wealth tax by another name.