Very interesting buddy. I've noticed this and people are making good amount from this IEO. I think it's a nice idea especially when they do the IEO on a major exchange like IDAX. Now IDAX and Exmarkets are some of the exchanges engaging most in the IEOs.
Yes, Recently I saw Exmarket becoming much popular among the IEOs. Maybe there are fewer regulations and easy listing in Exmarkets. but im not much sure about it. Whatever exchange project must be good to be a success even it is an IEO.