3% is a lot when compounded yearly. The article says that Marc Zuckerberg has 85 billion in assets. If we assume that's all in cash (it isn't), that he retires this year (seems unlikely, but whatever), that this measure passes and isn't repealed (etc), and that he lives to be 80, then over the next 44 years he'd pay 62.75 billion dollars in taxes. On top of inflation. Why would anyone let that happen, when they could prevent it by moving just a few miles in any direction? I'm sure there are a lot of places that are nicer to retire to than Palo Alto.

But you are right; income taxes were once seen as a really radical and unlikely idea. I don't think that means that we should resign ourselves to eventually be facing both income and wealth taxes.