The title says it. If i am running a CPM ad then it needs to be ensured that i dont get to see the ads at least, this is just running up the CPM count without any value, i think there should be some way to set it up that way. Thanks Shawn, else your ad system rocks, much better than when i used to use Adwords to display ads on DP, it is cheaper too (sometimes!)
I messed with not showing ads to the advertiser, but it was causing more issues than it was solving. It was adding a ton of processing overhead needed for every impression for one... but then it was actually causing support issues too where advertisers thought we were cheating them because they were getting charged for impressions but they never once saw their ad running. I'm in the process of working on some changes... it might be possible to do it in the future with some sort of opt-in for advertisers so they understand they aren't going to see their ads.