And how to they scam ? (Apart from the obvious- phishing.)
I read things like "multiply your bitcoin" and "free bitcoin". Sounds very dodgy, I stayed away. I'm surprised they can convince people to get involved.
The words you mentioned are the usual introductory words of an obvious scam site. Even that is an obvious scam, there are still many people who easily fall on that trap. Others knows that it's a trap but still taking the risk since they have the thinking that HYIP pays at first.
How come an owner of a company can double anyone's bitcoin and gives free bitcoin to all of it's users. Those people that is seeking any kinds of online income by any means are the one who always fall to that trap.
Scam is really part of online world even prior to the existence of cryptocurrency. It will be alive as long as the number of people that always hooked to that kind of system will not be minimized.