"We wanted to remind you that all Product Advertising API developers will be required to authenticate all calls to the Product Advertising API by August 15, 2009. We noticed that requests with your AWS Access Key ID are not being signed and, while you have more than 60 days until the date on which authentication is required, we are, as a courtesy, sending you this email to remind you of the new authentication requirement. Please remember that calls to the Product Advertising API that are not signed will not be processed after August 15, 2009. "
I'm guessing someone wasn't checking the e-mail account their AWS key is signed-up under,
So because Amazon didn't decide to require digitally signing advertising requests to start with, like they do for all the REST of their AWS customers, people have to be inconvenienced. Oh well...