Google AI with Jeff Dean [audio]

I was only ever at Google Brain, so I don't have direct experience at the other places you mention, but my impression was that there was somewhat more research freedom at Google Brain, particularly for theory. My impression of DeepMind was that it's relatively regimented and research is done in a very top-down way. OpenAI seems to have more of a focus on reinforcement learning (that's certainly done at Google Brain, too, but Google Brain does a lot of other things, too). I don't really know too much about Facebook Research.

From Jeff Dean on the differences between Google Brain and Deep Mind during an AMA last year:

https://www.reddit.com/r/MachineLearning/comments/4w6tsv/ama...

I don't know what title you gave it, but perhaps the HN guidelines can answer your question

https://news.ycombinator.com/newsguidelines.html

"…please use the original title, unless it is misleading or linkbait; don't editorialize…"

For the reason kilovoltaire gave: the site guidelines ask you to use the original title. It's standard moderation here to change those back when people don't do that.