Considering the fact that many exchanges have rather boring conditions for participating in sales of this kind, I mean IEO.
Please take a look at the comment above... there's some difference between these two stories... Like with any scheme, there are the ones who profit (little group), and the ones who lose (big group)!
It would be stupid to say that ICO, IEO, STO are the same thing... they have differences! But basically, it's raising money for a startup, where ICO is a simple project without any guarantees... IEO has some exchanges behind that backing up the project and they have a guaranteed listing... STO projects that have some guarantees on their project with some real possession (real estates, money, precious metals...)...
We have seen many scams with all of them! So this new IDO is something new that has one goal, to bring new investors, and probably most of them will be scammed, the same as all others before with ICO's, IEO's, STO's...