Chapman - 3:03 pm on Feb 24, 2013 (gmt 0)
I've been observing this "pull back" scenario for awhile now and others like HuskyPup have also mentioned it. Here's my take on it:
One of my sites relates to fine art and while I show hundreds of ads that are well targeted, I also end up showing ads that I look at as "confused targeting".
Most those ads are offering products or services of a non-online nature, with conversion categories I label as unlikely, impractical, impossible and illegal.
Any advertiser that has an online presence can have a conversion from anywhere in the world, however, if the advertiser is offering a service in a localized area, a conversion from well outside that area would be pretty much impossible. Example: a house painter or landscaper in Texas who's ad is clicked on by someone in Canada or Europe.
I also inadvertently show ads for heavy industrial trucks and equipment where someone clicking on the ad from overseas would make the conversion possibility rather impractical.
Many targeted ads I show are for art galleries where nothing is sold unless the gallery is visited in person. A click from someone very distant would make a conversion pretty unlikely.
And finally, some ads shown are for electronics equipment or technologies where a click from other parts of the world would create a conversion opportunity that would be illegal.
Now I don't know as much as I should about AdWords but, I think it is entirely possible that Google may now be putting two and two together and striking any clicks/revenue that may fall into category situations similar to those I've theorized on here and that "pull backs" may not only come from invalid or fraudulent clicks.