Should billionaires even exist?

You know what’s not cool anymore? Billionaires.

Their very existence is now the subject of political debate, sparked most recently by tax-the-rich proposals from two prominent politicians.

Sen. Elizabeth Warren (D-Mass.) proposed placing a 2 percent tax on wealth over $50 million and 3 percent on assets over $1 billion. Rep. Alexandria Ocasio-Cortez (D-N.Y.) said she wants to increase the marginal tax rate on those earning more than $10 million a year.

Their ideas went viral, starting a mainstream conversation about inequality and wealth.

This kind of talk has always existed among a certain group of hard-core progressives and left-leaning economists, but heading into next year’s presidential election, the idea that the super-rich should pay their fair share is gaining real momentum.