My experience (working at a company where someone reported an incident to HR) was, the folks responsible for the harassment were gone on Monday. Their offices cleaned out; the entire (2 people) department's duties reassigned; their name off of all lists and meetings. As if they never existed.

This is not incompatible with HR working for the company. They did their damnedest to protect the company from a lawsuit.

It's certainly something to consider; HR exists to protect the company. I suspect it depends on ensuring that the harasser is portrayed as the person threatening the company, rather than the complainant.

Indeed. Going to HR when the harasser has high value to the company might work differently...

http://www.sfweekly.com/thesnitch/2015/03/07/former-google-e...

I am not sure what you mean by "worked out for her." The manager is still at Google. She is the one that moved to a different team and eventually left.

If it ends up in court they're going to make the case that they can't be expected to address problems they don't know about.