Of couse that IEOs could turn out to a scam. There is no warranty that this can´t happen. But you can reduce the risk by choosing only IEOs on reputable exchanges - Bittrex and Binance.
Imagine fraudsters who conspire with a cryptocurrency exchange. And that they will steal $ 100,000,000 and then you yourself will figure out the credibility of authority. No one can give us guarantees of success. Keep this in mind when choosing a project and you should not believe the picture.