ColourOfSpring - 7:04 am on Apr 7, 2013 (gmt 0)
I've had two clients who did that for dev purposes. Wasn't my choice, but it was already done when I got there. In each case the dev site was walled off from Google.
And if Google *did* treat them the same, then they'd get just as much flack for breaking the standard.
It would be super-easy for Google to see if the www and non-www were different - spider them. If they're different, treat them as separate domains. If one redirects to the other OR simply shows the same content, treat them as the same, and certainly not "duplicate content" (if one does not redirect to the other). There should be no need to have two seperate "sites" in GWT for the latter case.