Performing a short is a sort of counter to to-the-moon talk. If you look at the mechanistic properties and costs associated with shorting, you can see how far the person buying the short thinks the value is from open market value. If you were to bet against the sun rising tomorrow, the market would "bet" to the contrary and the short would be cheap and accessible.

It's not craps gambling, it's like betting on a boxing match. The bookie odds are based on previous records and some valuation model, you only come out ahead in the long if you have a superior valuation model, insider knowledge, luck, etc.

Peterffy's letter to the CME is short and fun reading.

https://www.interactivebrokers.com/download/11-IB17-1145-tp-... [PDF]

His doomsday scenario is based on the Bitcoin price rising rapidly.

The CME's volatility limits would kick in, preventing shorts buying to cover their positions. This leads to "ruin" for them and the CME, and contagion for the real economy.

He has a good point, since losses on short positions are theoretically infinite, there's no way to put up enough margin for perfect safety.

Then this has happened -

https://www.bloomberg.com/news/articles/2017-11-15/bitcoin-e...

So it will be interesting to see how the pricing really works.

I did read that argument about real estate just the other day.

You can, saying you can't short it is false.