> If, however, we consider the fact that the aforementioned billionaire could borrow money using the appreciated stock as collateral — perhaps, say, to purchase

> If, however, we consider the fact that the aforementioned billionaire could borrow money using the appreciated stock as collateral — perhaps, say, to purchase a social media company — we might feel somewhat differently. After all, absent some mechanism by which the billionaire can be taxed, they can at least in theory defer ever realizing their gains by continually borrowing against their stock rather than selling any of it. This line is a great way to both throw shade and to make it clear that there are real-world examples of people currently exploiting this strategy. I wonder if it would be possible to just say, "If you have unrealized gains and aren't borrowing against them, then no taxes are necessary, but if you attempt to borrow against them, then they are treated as 'realized' even if they're not sold." That protects the interests of people who don't have the option to realize their assets (e.g. no liquidity event available) while still closing the loophole that allows billionaires to borrow against those assets tax-free.