Sueing a gigantic company requires lots of money, courage, and could leave you a marked person. It's not that easy of a thing to do.
Short answer is that their employment contracts probably don't allow them to sue. Almost all employment contracts contain binding arbitration agreements now.
If you are refering to me, I asked why she doesn't go to a lawyer... I had consulted lawyers many times in my life, but never sued.
No, I wasn't referring to that. I was referring to numerous comments on the original post of Susan Flower's blog on HN