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I do wonder if after the Ether "flash crash" recently (https://blog.gdax.com/eth-usd-trading-update-5d8142b5bdc1), if Coinbase / GDAX instituted some sort of "circuit breakers" on their exchange to prevent this type of thing from happening again. Bitcoin and the other cryptos, trades at a pretty low volume relative to their market cap, so if a lot of people we're trying to dump large orders this morning to take a profit at the new ATH, I could see that causing similar issues that they may have been trying to prevent.

Circuit breakers do not matter if other exchanges continue to trade the same currency. It would just cause the exchanges that do the circuit breaker to possibly hurt their customers.

The only effective circuit breaker is some form of synchronized method, but will the different exchanges cooperate? They really should put in circuit breakers this week across all exchanges so that when really bad stuff the panic doesn't destroy tons of people. It will be bad, but at least if the trades can complete and things unwind in a moderately slow fashion, it won't just 100,000 attempted transactions per second with random successes.

Maybe not, I'm just speculating that GDAX or coinbase may have added this as some sort of "sanity-check" in their system (regardless of the insane volatility in crypto right now!)

In the situation with ETH, a bunch of automated margin calls happened because of one large order on the books, dumping the price down to 10 cents! GDAX/Coinbase repaid a lot of people who lost money then, even though they didnt have to. They may now have some dumb heuristics that slow down trades / whatever if a bunch of large orders are going through, or price delta over a short time period goes too high. I remember looking at the charts today on GDAX and the 5 minute candle went from 20k open to 16k close before trading halted! I also heard from others that there were a lot of ~19k sells of 100 coins each on the books and executing.

So yeah, just speculating that this may bave been the case of someones boss at GDAX/Coinbase telling engineering "please don't make us do that again", after they ate the cost last time! :-)

> They really should put in circuit breakers this week across all exchanges so that when really bad stuff the panic doesn't destroy tons of people.

"Decentralized! Deregulated! But coordinate to protect us from ourselves, don't let us lose money!"

Haha, yeah I can't see the BTC crowd all being on-board with this.

That said, while I don't think the exchanges need to (or realistically could) coordinate on circuit breakers, I do think it's entirely reasonable for there to explore this type of mechanism on a per-exchange basis in the case of GDAX and other exchanges where margin is allowed, to prevent the whole "cascading margin call" thing that happened with ETH to happen again. That could take a lot of forms, including limiting the size of market orders to not eat 30% of the book, or not allowing 1 market order to trigger margin calls if (insert criteria here)

(That said, they could also just say "that's how margin and trading goes on low-volume, highly volatile assets" and technically be correct, but much like their decision to reimburse some traders, this is more of a business decision and wanting to keep your customers. Not sure what the "right" answer is.)

This is what I thought as well but haven't been able to articulate yet! It was actually on the opposite side -- a flash rise. I watched this happen and the order book on the sell side was getting extremely thin. The price rose thousands in minutes. I managed an 18k limit sell and bought back in at 16.5k

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