The below is my take on HYIPs.

"All HYIP is a scam and never invest a single penny in HYIPs"

Be it in a smart contract or not, none of the HYIPs can be trusted, even for a moment! That technical mumbo jumbo looks great on theory but when a HYIP promises around 20% of profit within few days, it's an obvious scam!

No real world business can generate a steady stream of such revenue to pay back its investors! So it's a cash rolling business at it's core! Not to be trusted and not to be recommended!