Without mentioning any names, I'm currently signed up with 2 "cloud" mining sites with minor investments of about 10$ each. I've managed to make back about half my investment (if you want to call it that) after about a week. These sites have since been flagged as scams and I think the only reason I may be seeing a return is due to the size of the contributions I've made. I'd be scared to invest more than that.
that is actually how they get you! first they show all signs of return and show a lot of good numbers to lull you into giving them your money and then they slowly turn the faucet off and after a while you realize you are losing money.
a couple of years ago they were even "giving away hashrate"! i even earned about 0.03BTC by claiming these free ones without investment before they realized they shouldn't let people withdraw without investing
