[fennecfoxen]

One key thing to note is that he's giving up citizenship before the IPO because he's going to be richer after the IPO and the US levies a tax on all your worldwide assets (not just your income) when you give up citizenship.

So if he ever wanted to move overseas to begin with (and avoid being taxed on the US while he lives overseas - a rather obnoxious system from all I hear), now's exactly the time to do it.