I've seen a couple of unimpressive RDFa demonstrations. They tend to involve either a beta search server from Yahoo! or a custom tool with ugly regular expressions. In spite of the quality of the presentations, though, I was sold on the value of using RDFa to embed metadata into HTML. But what good is metadata-rich markup when use case #1 (better SEO) is still absent? The tide is changing -- or, perhaps, has already changed.
Google now says that it supports both RDFa and microformats:
At Google, we believe in openness, so we are using two open standards to allow you to annotate structured data on your site: microformats and RDFa. Both standards allow markup of information on your pages. To ensure that Google understands your markup, we encourage you to follow the format of our examples. You don't need any prior knowledge of microformats or RDFa to use these standards, just a basic knowledge of XHTML.
Google lists at least a few microformats that they support, and offer a brief primer on RDFa and (apparently) how Google looks for RDFa information.
As I write this, I'm seeing Twitter messages pointing to O'Reilly's article discussing the same. It is clear that there is a new way for SEO....
Who says the Semantic Web is irrelevant?