GPG signing of emails has been around for more then 10 years but almost no one still does it. Now after a few break ins people are discovering something that they should had been doing 10 years ago, really this is a sorry state of things.
It's sad that a company like Google still does not allow GPG with there web mail interface, that said everyone knows why. The use of GPG signing would most likely eliminate Spam and this would change company's like Groupon forever. Knowing who sent a email makes email filtering easy and how do email providers give you something to make there product look better then others.
Even among top kernel developers we have such a slow rate of adoption GPG should have been every where 10 years ago, but still Spam continues to slow this rate of adoption. I am always amazed.