also, makes it easier to figure out who to kidnap and also who to blackmail.

Good point. But aren't there plenty of other public indicators of wealth?

No easier then driving around the nearest gated multi-million-dollar community. Or a trip through the Trader Joes parking lot.

There are some millionaires who choose to live modest and discreet lives. (or some I'm told). Publishing everybody's tax return does deny them the discreet part of their choice. That may be acceptable, but it is a real consequence.

As it is in Sweden.

While you are at it, might as well make voting rights proportional to taxes paid (perhaps plus a free allowance to allow poor people to have a say at all).