Well, imho, scam is not necessarily take away your money. If you give something (your time, your personal data, anything, your signature) because you are promised to be rewarded, but in the end the person/entity is breaking their promise, it might be called scam/fraud.
And BTW when you give your data freely they might sell it to some people, and many people willing to pay for personal data.
You are actually on point and exactly my mind you have represented because waste of time is not only when it involves financial bankruptcy. Making someone to shift or change from the original position of not posting at all (for instance ) is a fraud etc.