He recently posted a tweet stream opposing the bill, saying that if California passed the wealth tax it would be cutting off its nose to spite its face. When I speak to Mahan, he emphasizes the risk of California standing alone in taxing the net worth of billionaires. Because of the mobility of rich people, California does have real worries about the impact of a state wealth tax. Also, I don’t see why an exodus of billionaires necessarily means the end of Silicon Valley as the heart of tech innovation. A few years ago, some tech people moved to Miami, claiming it was going to become the new Silicon Valley.