Quickly testing the discovery that certain trigger keywords that relate to disasters kill contextual text ads in Gmail (via @ivanovitch):
A simple email to self designed to trigger auto-related ads. Ads didn't disappoint.
Another email, same copy, added "suicide 9/11" in the same font. Ads go away.
The third email, same copy, but "suicide 9/11" is in smaller and lighter font -- me thinking maybe trigger words can be an invisible part of the signature (click on the image for a larger one). Nope, ads come back.