I'm not sure why I'm so angry about this, but I am (maybe it's because I had just read another story about mistreatment of blog comments).
The director of social media for the Post-Dispatch (not some kid, either--he says he's been a journalist since 1982) used the IP address of a comment poster to notify his employer (a school), costing the person his (or her) job. The initial story is here, and his even more infuriating follow up is here.
This is so idiotic that I have trouble even responding. He didn't tell anything private, just how and where to find the guy?