If a bank wants to buy/sell/short (or whatever) bitcoins, how is it gonna justify these transactions to the regulators?
I am sure they can find many ways to cover their traces and appear legit but still find it hard to believe they can perform big volume illegitimate transactions (which can 'crush' bitcoin economy) without being noticed. Or it is just that the btc market cap is a joke for Goldman Sachs or JP Morgan...
I hope my writings make sense because English is my second language!