For a few days now my link with 5% weight is getting 4,000-5,000 impressions and my link with 20% weight is getting 300-400 impressions per day. Why would this happen?
Your 5% page link has been lucky enough to get into the cache of one or more big page count sites. Probably big page count and high traffic sites.
yeah.. both 4,000 and 400 are not huge numbers. I have ads that get 50k+ impressions. The reason is most likely what Arnica is saying... about the smaller ads being lucky to get in the cache of high traffic sites. Also, take into account that a good chunk of the co-op sites are made up of AWS sites and directories which have very little daily traffic.