I've previously reported on this blog that CDI/ Chungdam Institute was one of the better hagwon chains to work for. There were really no bad reports about them around the internet, and I even went as far as having interviews and considering working there a few years back. However, some bad things are going down now, with lawsuits and such. Check out the link.
Now, in the interests of fairness, as far as I know, they have an option where you basically are a freelancer. You work national holidays, you don't get vacation, etc, etc. But, you get paid a high hourly rate. So perhaps the people in question signed this type of agreement and didn't read the fine print closely enough. Who knows. Everything with a grain of salt I guess.