As an investor, i cannot participate in IEO conducted by small and new exchanges. The main reason why IEOs are preferred to ICOs is because they are more prone to scam than ICOs, and this is because the exchange validates its legality with their reputation. Imagine Binance or any top exchange conducting a scam project, it will jeopardize their integrity, and these exchanges do not want their integrity in question, so they only offer legit and promising projects IEO. New exchanges do not have the reputation to validate a project, they are just after the profit, SO they might promote a scam project either intentionally or unintentionally.
For now the IEO includes a trusted way to invest in new projects. But there is a possibility that the IEO will also commit fraud. Not necessarily finished the IEO project, they will be publishing their tokens at the exchange it. It may be that they don't publish there, or slow down the listing process. Because I see there are IEO tokens that slow down exchanges.