(when all of the existing exchanges click off one by one just like mtgox did , each one having already/all along taken all real customer deposited fiat off the exchange and socked it away in swiss/caman banks then of course claim to be hacked and then proceeding to dump their previous customer's real stolen bitcoins into the next doomed fraudulent exchange so they can get that money from those actual stolen bitcoins as well as the stolen fiat and price goes to $0 as the last standing exchange implodes ... during which time the network will freeze at some point due to overscaled industrial mining operations shutting down en mass faster than difficulty can adjust down ... that's how we'll know the bottom is in)