For those who mention low EPC but didn't mention CTR, are you seeing a higher CTR when you see the low EPC?
I keep beating that drum but it's the way ours goes. The last two days have been fair with high-normal CTR and high-normal EPC but most of the time the EPC goes down about 35% when our CTR reaches a certain %. It seems to me that when site visitors are more click-worthy the advertisers know they can lower their bids because they will still achieve their goals.
EDIT: Mainly US traffic on all sites.