For all those posting variants of "It's no different from stocks", this is answered in TFA but even more clearly in the Paulo Santos article linked from it[1]. Editing it down a bit,
> ...overwhelmingly, bitcoin is traded on bitcoin exchanges... So here's the thing: Each of these markets does not communicate with the others. [That] ... means that buyers/sellers on each exchange are reliant on bids/asks exclusively from other members trading on the very same exchange.
> Now, that doesn't seem all that different from what happens with stocks in countries like the U.S., with all kinds of markets and ECNs, does it? But it really is massively different... because with stocks, a broker can quickly reroute his orders from one exchange to the other. The depositary/custodian of his stockholdings is not the exchange. With bitcoin, it's different. The exchange is also the depositary of one's bitcoin holdings ...[describes the difficulty and delay of moving BTC from one exchange to another, also discussed at length in TFA] ... The result of this highly inefficient market structure is that the same asset (Bitcoin) trades at significantly different prices from exchange to exchange...
So with stocks, if you want to buy or sell shares of AAPL, the price will be essentially the same whether you talk to Schwab or to eTrade, and if it isn't the same to within a penny, a script somewhere will take advantage of the difference to make money by buying from one and selling at the other _in seconds_ -- arbitrage which is not possible with bitcoin exchanges owing to the transaction delay and fee.
TFA also makes the important point that there is no regulation whatever of bitcoin exchanges, and that also makes them very different from the likes of Schwab.
[1] https://seekingalpha.com/article/4130380-bitcoin-series-adde...