A few minutes with a calculator will show anyone why Cex.io can never be profitable when used just for mining. The price of a gigahash falls faster than the bitcoins that gigahash can generate during the same time, even if you end up selling the investment plus keeping the generated bitcoins. And then there are the fees.
The only people who make money on cex.io are the ones who got in very early and the traders riding the price downwards while extracting value from price swings. Everyone else loses.
Wrong i'm afraid, take a look at GHS price charts, been upwards since begin of May, interestingly it seems to have disconnected from it's inverse relationship to difficulty.. Take a look at the Futures contracts CEX.IO made available (FHA & FHM) again profitable opportunities.
If you ONLY buy cloud hashing sit back and expect a profit, then the only outcome you'll get is disapointment.
Trading GHS and mining combined can be profitable if you educate yourself and treat your trading as a business in terms of your approach.