I'm a big fan of inline structured data like RDFa because it makes it easy to share information between sites. For example, if my research institute listed my speaking appearances with RDFa, I could just use Views to display those presentations on my site. Instead of getting the list from my MySQL database, Views would use the external Web page as its "database".
I'm also a big fan of HTML5. It is a big step towards a more exciting, more usable, and more developer friendly Web.
Drupal has made commitments to both, with its support for RDFa in core in Drupal 7 and its move towards HTML 5 output in Drupal 8. That's why I wanted to give the RDFa and HTML 5 compatibility a test drive, starting with my own site.