This only works if stocks go up, up, and up. Otherwise they will have to realize gains at some point to pay off the loans.

I don't get why we have to jump all the way to a wealth tax, could they not just force asset backed loans to trigger a tax? This seems way more targeted and we won't have people assessing what everyone is worth. I think it would avoid some unnecessary precedent setting. They could put the impetus on the billionaire taking the loan to state what the assets are worth and related gains.