For example, no one knows Satoshi's addresses, but they are rumored to contain upwards of 1,000,000 Bitcoins.
So, he's a billionaire on paper. If he were to sell his BTC, how much would he expect to lose due to the associated crash in the BTC marketplace?
Why would he need to? If he is able to spend his bitcoins for whatever he needs he should be fine without selling anything.