As Adsense publisher, you should have received this copy of email from Google, as well as being displayed this page by the first time you login to your account yesterday, after the announcement.  With the new email notification preference, Google Adsense want you to be aware of any changes or improvement, new offer on the product as well as the updae on it policy.

You can choose ypes of emails you want to receive by login to your Adsense account,  My Account followed by Account Settings.

We’ve updated our email notification preferences.

In addition to the newsletters and surveys you’re currently signed up to receive, you can choose to receive messages like personalized optimization tips, webinar and event invitations, and news about special promotions and giveaways. Because you chose to receive newsletters and surveys when you signed up for AdSense, we’ve updated your preferences to reflect the two new categories for newsletters and market research. Please take a minute to look over your options, then visit your Contact Preferences page to confirm your selections.Customized help and performance suggestions
Receive suggestions from members of the AdSense team for changes you can make to improve performance and earn more from your site.

Newsletters
Receive newsletters with optimization tips, best practices, and other information to help you get the most out of your Google AdSense account.

Google market research
Receive invitations to test new features, surveys about Google AdSense, and opportunities to provide feedback about your experiences.

Special offers
Receive news about AdSense promotions, events, and giveaways.

Information about other Google products and services which may be of interest to you
Receive news and special offers from other Google products such as coupons from Google AdWords and other offers we think will benefit you.