>>but might not be illegal, since simple numbers like a dollar amount can’t be copyrighted, and AFAIK there is no other legal impediment to Google doing what they did (IANAL).

Forbes for one spends a LOT of money hiring people to try to estimate the net-worth. So it is a number--but one that someone paid a lot of money to get it. Illegal? Maybe. Not-ethical? Very much so IMO