> And really what is the practical difference between having $20m and $2b? Sure you'll have nicer houses and more of them. You may well have a super-yacht at that point. But who cares? I know I don't.

At $20m you can shape your own world, and your family's. But at $2bn you can change society. You can buy a lot of influence both by directly spending the cash to accomplish goals and by bribing politicians to act on your behalf.