I used to think the black market was the sleazy underbelly of the country, where you risked your life going there, and getting ripped off was part of it.
However, the black market isn't anything like that. In that market, your reputation is everything. You get what you pay for, and you pay for what you get.
That sleazy area is the white market with con men looking for marks.
On bitcoin vs gold... Gold has lost its value because most of it is owned by banks and rots-children. We do not have any idea how much gold is in the hands of these big players. So we can not gauge the value of any transaction... or, put another way, all of a sudden, someone could flood the gold market crashing the price of gold for years. (its been done)
Gold is also not very useful. Sure, its pretty. But, doing transactions in this internet age, gold just doesn't do squat. In Zimbabwe gold is being used for transactions, only because it is being mined there, and there is an external market for it.
Further, crypto-currencies has just gotten started. Blockchains will replace the entire financial industry. All of it. Wall street will be a row of empty buildings.