When people should have been suspecting Whirlwind to be scam is when they began anonymity mining or something with 12% APR. I do not know much about it but it is like a way people will leave their bitcoin on the centralized mixing service. Many people will be affected.
This same applies to exchanges as to Whirlwind: Not your keys, not your coins. So everyone can decide for themselves to take the risk or not.
Another way that people can think of is when they began paying using note public key to the Whirlwind participants on this forum. Funds are paid from note public key into note public key. It would have been better if it is paid to individual bitcoin addresses on their self hosted wallet.
It is always better to get your coins directly in your wallet. I do not know if anyone complained about the chance? But this procedure is also often done at campaigns from casinos. Payout directly to the user account. It is always about trust. And Whirlwind has abused our trust completely.