no one knows exactly where the scam and what is not, except maybe he has the 6th sense may be hehe, the point back to dirikita each, we do something we really understand and we know. my advice is more careful, because it all depends what we do as well. yes so lah I never experienced it because I myself was not careful.
Somebody told me that when I invest something, I must use my heart rather my mind. In terms of scam? I never scammed since I was started here in bitcointalk and cryptocurrency because I am not yet earning lots of money but I think I already scammed by project ( I just don't know if it will pay my service). Someday I will try to invest and trade altcoins and bitcoin, I will conquer my fear of being scammed. You are right! We don't know the day and how we will be scammed but checking of backgrounds and personality behind altcoin helps us to keep calm that our coin is in the good hands.