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.
nothing any project are safe for investor, all of investation way must have a risk, but trying to invest in cryptocurrency like IEO give us a guarante from xchange and make this project are running as usual, and certainty will listed on market