I came across a recent update by VP of GDAX Adam White stating that GDAX will be crediting their customers that had their ETH Stop Loss triggered or their Margin called in light of the June 21 rapid price movement that happened. The good thing is all those who were able to scoop cheap ETH gets to keep theirs.
I find this act very noble. This is basically them giving free ETH to those people who were speculating and got their asses handed over to them by someone or something that tried manipulating the market. By showing they care about their customers warrants them a pat on the back. Does the users who were affected deserve getting liquidated or margin called? Of course! It's the price you pay for taking the risk and I doubt if this happened in Poloniex everyone would just say "that sucks bro" then move on which makes GDAX decision more admirable.
Now, from what I understand from what happened it should take Millions of dollars to make that event happen. In the ballpark of around $4 Million worh of ETH which does make it look like Market Manipulation. Which makes GDAX's action to this surprising and again admired. They showed commitment to their customers and I expect influx of people using their platform because of this wise decision.
I normally don't use GDAX (only used them once when I wanted to buy IOTA) but will take a look at doing more business with them from now on.
Reference :
https://blog.gdax.com/eth-usd-trading-update-2-216a3b946ef6?gi=19a59c6e0fa8
PS: Obviously I'm not a paid Shill as you can see from my newbie form of writing. I just wanted to give my hats off to them and wanted to write my story off of them as I wanted to post some good news in this Wild Wild West of this Cryptocurrency space we have.