Google Web Authoring Statistics

This is actually about a week old, so pardon my procrastination. Google has released a Web Authoring Statistics, "In December 2005 we did an analysis of a sample of slightly over a billion documents, extracting information about popular class names, elements, attributes, and related metadata. The results we found are available below. We hope this is of use!"
The data is presented in pretty graphs. Might be a useful resource for your SEO optimizations project.