netmeg - 3:15 pm on May 9, 2013 (gmt 0)
Google "smart pricing"
Also, Google always tells us that the highest paying ad is the one that's showing first on your page. But what if for whatever reason, the user clicks on the LAST ad (which is presumably among the lowest paying) on your page? If you use more than one ad unit, that's always a possibility.
Clicks is clicks is clicks. I get .01 clicks and I get 9.00 clicks. Obviously I prefer the latter, but the former add up too. I'll take them all.