Ask HN: Are there any tech billionaires who just dropped out?

It seems like most people who got a billion (or even just high multi-million) dollar windfall from an acquisition (like Eduardo Saverin, Peter Thiel, etc.) are becoming "angel investors" and stay active in tech or related endeavours.

But are there any similarly rich guys who just said "f*k it all" after cashing out and are now living off their cash (which should last them and a couple of future generations of offspring)?