Matt Cutts of Google said in his PubCon Keynote a month or so ago that Google would be stepping up their notifications of spam issues and they indeed have.

In early December, Google started sending out notices of doorway pages via Google Webmaster Tools and now webmasters are receiving more spam notifications.

A paid WebmasterWorld thread has reports of Google warning over “unnatural links” and a Google Webmaster Help thread has reports of warnings over “cloaking”. Both are against Google’s Webmaster guidelines.

Unnatural Links warnings look like this:

Cloaking Warning looks like this:

Have you also received quality guidelines emails or notices in Google Webmaster Tools recently?

Forum discussion at paid WebmasterWorld and Google Webmaster Help.