If you can combine trading with mining rewards like on CEX with their GHS, then that can be profitable. I did an exercise and noted the outcomes in this thread https://bitcointalk.org/index.php?topic=805526.0

They way I currently view it is the mining rewards are a small part of the overall reward, the buying and selling of GHS providing the main potential profit.  It works for me, might not be for everyone. The days of just buying a cloud contract and sitting back watching the BTC roll in to ROI are gone (if they ever were there in the first place).