[lmm]

Stocks - at least, blue-chip stocks - are usually thickly traded. The full set of shares outstanding does get bought and sold, at prices that usually remain roughly reflective of the market price (e.g. Dell being taken private, for a recent example). There are stocks that trade much more thinly, and this kind of absurdity can happen there, e.g. Bigfoot Project: https://www.bloomberg.com/view/articles/2016-08-18/bigfoot-r... .

So there's no clear bright line between "legitimate market cap" and "silly market cap". But there is a quantitative difference, and it's worth thinking about how deep the order book is when you see these "market cap" calculations being thrown arond.