They're actually not a scam. I thought that too, but when LTC started to go up, my contract paid off. I got the least expensive one. There's a guy on steemit that just went to visit them and took a video...they're in Iceland. It depends on how you allocate your hash power and what contracts you buy. It takes a little research. Follow Boxmining and look into it if you really want to do it. Use his bonus code. Choose a blockchain that is growing and isn't already huge (like BTC or ETH).