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.
This is just the beginning in future we may see more kind of scam project event through promoted by the crypto exchanges because there are lot of shit exchanges start doing promotion of new crypto project which cannot be compared to the reputed exchange promotion, so do your own research and invest if you convinced enough to invest on the project.