Don't use CEX.io for anything, they are scammers and continue to scam people.
cex.io has always scammed since their founding, I will go over my experience with them and also a link to some redditors exp with them recently.
Lots of scam accusations going on over here --- https://www.reddit.com/r/btc/comments/7qsndd/update_on_my_missing_usd_34000_with_cexio/
cex.io as they get banking form Crypto Capital the same company that Bitfinex gets it's banking from.--https://medium.com/@mathias_61938/the-man-behind-the-curtain-81ecf49fa339
My story
Back when they sold hashing power for mining they released a futures market on hashing power, which completely tanked hashing power price per ghz by over 50% within 12 hours and more than 90% over a few days(hashing power is the cloud mining contract you buy for mining). So what happened is that EVERYONE who bought hashing power and was cloud mining with CEX got completely f'ed and lost big time. There were people who don't pay attention every day to their cloud mining and they logged in days later to find they lost 90% due to the release of mining futures. The mining futures were directly betting against the mining hash power(kind of like shorting a stock).
They gave no notice to this happening. People collectively lost hundreds of thousands of bitcoins due to this, CEX was a pretty big mining operation at the time and got up to 45 to 50% of total hashing network power. Fast forward to today and they reopen and re-brand as an exchange and nobody is the wiser apparently.
I lost 40% of 9 btc back then in one day due to their futures bullshit. I got out same day luckily. They basically did it because they lied about owning the ACTUAL MINING EQUIPMENT, but they really didn't own it. They were renting clouding mining from somewhere else and actually selling it back to us. They eventually started losing money and tried to screw over everyone else by making futures(to short against their own users).
Did they ever get prosecuted for that bullshitery? Anyone know? As far as I am aware nothing ever happened to them and not many people talked about it for some reason.
To add to that, the CEO admitted they didn't even have mining hardware that that it was 3rd party the whole time, AND they admitted they turned of people's mining and didn't turn it back on(you had to manually do it). So if you didn't notice they turned your mining power off, your hashing power wasn't getting you anything.
From the article where he admits it
"Smith tells me that CEX has no hardware of their own, and everything traded on their exchange occurs through third-party hardware companies that have chosen to remain nameless. That isn't so much of a revelation as much as it is a fact that went unnoticed by many. The knowledge likely won’t quiet those who are complaining about a perceived lack of transparency. The website’s cloud mining page says nothing about hardware being held by third parties.
Really, nothing has changed for end users. If you own GHS, you can simply turn it back on and continue using the hashing power as you were before. People may feel as though CEX is looking to profit off those who don't bother to turn their GHS back on, but for the individual who is fearful that CEX is trying to get one up on them, the solution is to simply to turn it back on."