I haven't been long in the Co-op, but when I started I was getting around 1100 ad impressions per day. It has gradually fallen off to between 300-400 per day. My weight fluctuated a little bit, from 12k to 11k, then 10k and back to 11k. I'm not going to complain about that as I know it's just the way things work with the Google API. Is it the case that a new member gets X number of ad impressions per day, based on their weight, and this is then adjusted to reflect the number of ad impressions which appear on their own site? In other words, if their site gets fewer visitors than expected, is the number of times their own ads appear on other Co-op sites reduced?
The figures for yesterday (15th) returned to around the same as the previous impressions figures. I'll keep my fingers crossed that the numbers won't drop again.