You're right, I haven't heard of actual quotas either. I just got a bit loose with using the parent commenter's terminology.
I agree on the subtle and implicit bias issue as well. I wasn't trying to be exhaustive, but that's a big enough issue that it ought to be specifically mentioned.
I also have never heard of a company actually having quotas. What I have heard is people gathering statistics and saying, "Hey, this looks pretty bad. What are we doing that might cause this? What can we do to fix our [generally unconscious and unnoticed] biases in our hiring processes?"
[1] http://www.washingtonpost.com/news/wonkblog/wp/2014/12/08/ac...