ember - 5:15 pm on Feb 1, 2013 (gmt 0)
I was told by an Adsense team member that if you run your ads through DFP, it allows you to do that.
Not exactly. You can set a minimum threshold, but if there are no ads to meet that, then cheaper ads run. Either that or no ads run, depending on how you set up dfp. I am no dfp expert, but that's been my experience.