Payment terms for a real cloud mining service operated by an actual ASIC manufacturer:
Payout calculation
Payouts are done daily.
The payout rate before fee substraction is 25 / (difficulty * 4.295) BTC per unit per second.
The fee is 1.89*10^(-8) USD per unit per second. It will be substracted from the pre-fee payout rate. The exchange rate is based on bitstamp 24h average.
The total seconds of each payout is:
1. in the first payout, 3,600 * 24.
2. During normal payouts, the number of seconds during the most recent payout to this payout.
If there is a difficulty change between two payouts, the due payout will be calculated based on two different difficulties and their corresponding time intervals.
If the calculated payout after fee substraction is less than or equal to zero, the contract will be suspended. If the number of subsequent days suspended reaches 10, the contract terminates.
Payment terms for a cloud mining ponzi:
A - B = C
That says it all really.