Usually, anything that promises abnormally high returns is a scam. If they have a lack of information or bad English on their site/FAQ's, they're most likely scams.
Agree on this ...expecially on the first sentence. Proper english doesn't mean anything to me if they are promising the impossible.
My suggestion in these cases is this one: try to substitute $ to
BTC and ask yourselves and the real life to the web. Would believe someone telling you in real live give me your $ and I will give you back double/triple or whatever return they promise?
BTC and the web are just "things" people use in their real lives...