I setup a FB CPM campaign over a year ago, at a very low CPM bid, and basically forgot about it because my ad never outbid other campaigns. Then in September of last year, it started spending the daily limit.
I initially thought that FB was fudging the black box to extract more money out of advertisers before the IPO to make itself look better on paper. But, now I'm more convinced that the market for FB advertising has dried up a bit, confirming your comment.
It sure can't be explained by the fact that ad delivery systems are seldom static and are continually being tweaked based on the latest research....oh wait, it can, but you just go ahead and pick whatever is expedient with your beliefs.
I initially thought that FB was fudging the black box to extract more money out of advertisers before the IPO to make itself look better on paper. But, now I'm more convinced that the market for FB advertising has dried up a bit, confirming your comment.