Google has released a new way for them to notify webmasters of possible penalties with their web sites.
Now, if you are in violation of Google's web search TOS, you will receive a notification via Google Webmaster Tools, just one more reason to sign up and validate your site with Google Webmaster Central. If you are in violation, you will see a message indicator in the message center. It looks like this:
And if you click on a specific message, it will probably include content about search quality issues with a specific site. Google said, over time, they will also include non-search quality issue type of emails. Here is an example of a quality issue message:
If you login to your account and do not see a message, it does not mean you do not have quality search issues, at least today. Google said, "the number of sites we’re contacting is small, but we hope to expand this program over time." So, over time, hopefully all verified sites with quality issues will show a message in the message center.
Danny Sullivan explains that Google still may send out email notifications, but that will stop shortly. There is a current issue where if you get an email notification, and are not verified within Google Webmaster Central - you won't be able to see the message even after verifying your site. But Danny said they will be fixing that issue shortly.