You mean CPM ads only or CPC based on CPM ratio? Cost per click ads is much more popular and people are more willing to buy it thru traffic brokers like
TrafficHolder.com ,
TrafficShop.com,
EroAdvertising,
JuicyAds (quality banner traffic).
Also some tgp networks like
www.yobt.com and
www.trafficgear.com are buying it on a constant basis.