Classic example is doing a startup (and failing to take off). You have a very large nominal wealth, but you practically bankrupted yourself, because as a founder you probably spent all your money to try to raise more funds, or on sales, or on product development.

Yes, the Forbes list is different.

And yes, erikb's point about being a billionare is strange, because not many people would consider anyone a billionare just because someone funded a company with nominal value 1B$.

However, erikb is right, that rich people have cheap access to enormously powerful success multipliers. (They can very realistically - almost literally - get a cheap loan from any of their dad's neighbour, or get in touch with anyone, and so on.)

It's also hard for me to see where our experiences diverge so much that we can't understand each other. Maybe you don't know that billionaires are not having this billion dollars on their bank account, but instead it's a calculation of assumed ownership of stock, houses, derivates etc?

If you have a billion dollar on a bank account with a bank that would cash that amount of money, then I'd say yes you are rich. But the Forbes list is mostly guessed values that are used in calculations, based on real but unknown values that may change a lot between one day and another.

I hope that was the point. If not give me some hints or explain your point of view more detailed. I wouldn't be surprised if we find out that we actually share the same view but express it differently.