The idea of cloud mining is wrong from the beginning, so they say: "Hey, dude, we offer you X hashrate for Y dollars for Z time, buy now and start mining from day 1!". Nobody who buys this never counts on raise of difficulty and global hashpower.
In case of Zcash, everybody had an option to test speeds of existing software before actual start using testnet, and now people start telling that they were fooled by cloud mining services who sold them 5 Sol/s for 5000$. If you have that amount of money free to invest, you'd better make some investigation before throwing them to the wind.
If just stop and think, who in his mind will sell their hashing power on fair terms? If you were cloud mining service owner, just count investments you need before actually even starting mining operations:
1) Mining hardware location, it should be hangar-like building with efficient ventilation and cooling systems, rent such a place or build it on your own or rented land.
2) Maintenance personnel, your employees who will monitor and fix your equipment 24/7, they need to get paid every month/week, it's quite a hard work if you ever tried to keep running even 50 rigs at one time in one place.
3) Equipment, you need hashpower that you'll sell in future, ASICs, GPUs, shelves for equipment placement, and you need lots of that stuff.
Minimum requirement reached, you're ready to start selling your hashpower. Will you payout fair to your buyers? No way! Now you have to pay for electricity,internet,salary for your employees, replace faulty hardware and so on. If you count precisely, even giving out 1/5 of actual hashrate income to your clients will be unprofitable.
So, the only thing you're doing buying cloud mining services is paying somebody's electricity bills for crumbs from his table, without even possibility of reaching positive ROI someday.
Only cloud mining option that is worth attention at the moment, for my opinion, is genesis-mining SHA-256 lifetime contract, it roughly has a possibility of reaching positive ROI in 3-5 years (if Chinese won't spike hashing speed again), other seem like Mavrodi's MMM Global, or how it's called now?