If it is too good to be true it probably is not goes the old adage and it is as true today as it was in the past. When people are promised higher yields on their deposits, they are often swayed by greed.You should be wary of wallets that offer returns if you keep money in them or if some investment program gives you way more returns than the prevalent market rates.
A lot of mining operations are alleged to be scams but to narrow down the definition mining scams can be described as operations, which take a fee to mine Bitcoin on your behalf but never deliver. Cloud mining particularly has been in the eye of the storm.