My sample HTML page has this, but Sindice, which uses Any23, didn't read my namespace correctly. I narrowed it down to, and changed accordingly, the XSLT template "tokenize2" in the rdfa.xslt stylesheet. The template expected "ns1:http://example.org/ ns2:http://example.com/" (no spaces between prefix and namespace URI) and did not normalize whitespace, like linebreaks (although I'm not sure that broke the functionality).
I use Any23 0.6.1 locally, but http://svn.apache.org/viewvc/incubator/any23/trunk/core/src/main/resources/org/apache/any23/extractor/rdfa/rdfa.xslt?revision=1231556&view=markup shows that the template is the same in the trunk.
A possible problem may be that the new template will not accept the non-spaced namespace definitions, like you can find in the RDFa produced by Best Buy. A further improvement to my template may be accepting both namespace definitions with spaces and the ones without.