Anger at extreme wealth is turning into real tax proposals, which is bad news for billionaires and potentially good news for people who have watched their share of the economy shrink.

• California voters will decide in November on Prop 40, a one-time 5% tax on billionaires' wealth, and tech money is spending heavily to kill it.
• The core argument: the very rich are getting richer far faster than the economy grows, so their gains come out of everyone else's pockets through higher house prices, stock prices, and debt.
• Even Chamath Palihapitiya says Silicon Valley has lost its way and now chases money above all, which is why public hatred keeps building.
• Economist Gabriel Zucman argues the "they'll all just leave" objection is a policy choice, not a law of nature — taxes can be written so moving away doesn't help.
• Prop 40 may still fail, less because voters oppose it than because California unions are fighting over where the money would go.

Outlook: Even if California's measure loses, wealth taxes look set to keep returning to the ballot in the US and Europe, where polls show overwhelming public support.