"8 USC § 1182: (E) Former citizens who renounced citizenship to avoid taxation
Any alien who is a former citizen of the United States who officially renounces United States citizenship and who is determined by the Attorney General to have renounced United States citizenship for the purpose of avoiding taxation by the United States is inadmissible."
If he did it for tax reasons, it would make a lot more sense for him to do it pre-IPO announcement, or really as early as possible, as the amount of exit tax he's liable for is based on an estimate of the value of his assets. As the article mentions, it's easier to argue that number down when it's a private company.
I am sure Eduardo will be all set. He will be back in the U.S. and will avoid $1-$2B in taxes.
So, if the US government cares, this person could be denied entrance to the US.
There literally is a point where you can't spend the money fast enough (on objects for personal use) to lose it. You can lose it doing dumb things in financial markets or with a business, but if you have $3 billion dollars it is impossible to spend it fast enough to lose it. You can burn $40 million down to see (see: most musicians and athletes), but not $3 billion.
Even earning 2% interest on 3 Billion (i.e. Treasury bonds or something nearly risk-free), you can make $165,000 A DAY.
So buy 3 cars today, and tomorrow, and the day after that, and the day after that. You just can't do it.
So whats the difference between $2 billion and $3 billion? Not all that much. (And I don't believe he is avoiding a billion dollar tax bill, he still has to pay some level of exit tax).
But the difference between being able to come to the US and not coming to the US is significant. What if he wants to go to a movie premiere in LA, or skiing with friends in Aspen, or going to Warren Buffet's annual investors meeting, or seeing a VC in Silicon Valley? You can shop anywhere, you can vacation anywhere, and you can eat anywhere. But some events only happen in one country or another. Some partnerships only happen in one country or another.
That's obviously assuming the IRS decided he renounced his citizenship for tax reasons and he is banned from the US.