I am in a programming mood.
I put a little table at the bottom of the Calendar/Category page that shows the average number of hits per event along with historical data. For example the Salt Lake Shopping category page shows 26 archived events which received 4175 page views ... an average of 160 page views per event.
Most of the page views are the GoogleBot or other web crawlers. My advertising revenue is a little under $1 for thousand page views. This section of the site has probably generated about $4 in revenue over the last three years.
It is not a lucrative business.