For those heavy Google AdWords API users and developers, did you know that the proximityTargets do not work properly for traffic estimation?
A Google AdWords API Help thread has Eric Koleda from the Google AdWords API Team who confirmed the issue. He said:
There is a known issue where proximityTargets aren't processed correctly for traffic estimation. I don't believe this problem will be fixed in the near term, so I would recommend you look into other geo targeting options.
So Google is aware of the issue, but clearly it is not a priority to fix.
Forum discussion at Google AdWords API Help.