This is probably going to be to complex but it is sort of topical to this.
Lumo has put up a review of the paper Hawkings has in pre-print at the moment and many of us are digesting.
http://motls.blogspot.com.au/2015/08/stephen-hawking-solves-information-loss.htmlI found the article interesting because Lumo basically and forcefully argues that gravity must be Quantum in nature. The article was actually more interesting than Hawkings paper.
For my part I hadn't even realized and thought about a couple of things he says, so I am currently trying to debunk them because they are important. He would probably berate me as much as he does poor Sabine because I have always left open the possibility the gravity is entirely classical.
His example of one boson in Stockholm and one boson in Boston is driving me nuts, I can't break the lack of localization. I think I just took the RED pill and I now officially hate string theorists and I am going to hunt them all down.
Lumo has put me in Dave's position I can have QM OR I can have a classical gravity field but I can't have them both.