The source data is about 130K text/html pages, randomly selected from the list provided by dmoz.org and downloaded about a year ago.

Then I looked for all HTML comments (found by an HTML5 parser) containing a substring "<rdf:RDF.*creativecommons.*/rdf:RDF>".

132 pages contained such a comment.

(Only 16 pages contained a non-commented <rdf:RDF> element seen by the HTML5 parser; I didn't include those pages in this analysis.)

Ignoring version numbers and country codes, the number of usages of each license are:
     13 http://creativecommons.org/licenses/by/
      5 http://creativecommons.org/licenses/by-nc/
     39 http://creativecommons.org/licenses/by-nc-nd/
     47 http://creativecommons.org/licenses/by-nc-sa/
      4 http://creativecommons.org/licenses/by-nd/
      6 http://creativecommons.org/licenses/by-nd-nc/
     13 http://creativecommons.org/licenses/by-sa/
      1 http://creativecommons.org/licenses/nc-sa/
      3 http://creativecommons.org/licenses/publicdomain/

8 pages had a <License rdf:about> but no permits/requires/prohibits elements inside it.


There are two with inconsistent licensing requirements. (They look quite like somebody modified the permits/requires lines without modifying the license URI.)

http://www.ashrita.com/
Says that by-nc-nd permits DerivativeWorks:
    <rdf:RDF xmlns="http://web.resource.org/cc/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> 
      <Work rdf:about="http://www.ashrita.com/index_html"> 
        <dc:title>The Most Records</dc:title>
        <dc:description></dc:description>
        <license rdf:resource="http://creativecommons.org/licenses/by-nc-nd/2.5/" />
      </Work>
      <License rdf:about="http://creativecommons.org/licenses/by-nc-nd/2.5/"> 
        <permits rdf:resource="http://web.resource.org/cc/Reproduction"/> 
        <permits rdf:resource="http://web.resource.org/cc/Distribution"/> 
        <requires rdf:resource="http://web.resource.org/cc/Notice"/> 
        <requires rdf:resource="http://web.resource.org/cc/Attribution"/> 
        <prohibits rdf:resource="http://web.resource.org/cc/CommercialUse"/> 
        <permits rdf:resource="http://web.resource.org/cc/DerivativeWorks"/> 
      </License> 
    </rdf:RDF>


http://www.tecniferio.com/
Doesn't say by-sa requires ShareAlike or that it permits DerivativeWorks, but does (non-standardly) say it permits CommercialUse:
    <rdf:RDF xmlns="http://web.resource.org/cc/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
        <Work rdf:about="">
            <license rdf:resource="http://creativecommons.org/licenses/by-sa/2.5/es/" />
                <dc:title>
                    Tecniferio
                </dc:title>
                <dc:date>
                    2004
                </dc:date>
                <dc:description>
                    Diario en castellano sobre cultura y sociedad
                </dc:description>
                <dc:creator>
                    <Agent>
                        <dc:title>
                            Juan Díez Blanco
                        </dc:title>
                    </Agent>
                </dc:creator>
                <dc:type rdf:resource="http://purl.org/dc/dcmitype/Text" />
        </Work>
        <License rdf:about="http://creativecommons.org/licenses/by-sa/2.5/es/">
            <permits rdf:resource="http://web.resource.org/cc/Reproduction"/>
            <permits rdf:resource="http://web.resource.org/cc/Distribution"/>
            <requires rdf:resource="http://web.resource.org/cc/Notice"/>
            <requires rdf:resource="http://web.resource.org/cc/Attribution"/>
            <permits rdf:resource="http://web.resource.org/cc/CommercialUse"/>
        </License>
    </rdf:RDF>


There is one that is not well-formed XML (it has random <p> tags inserted):

http://www.icannchannel.de
    <rdf:RDF xmlns="http://web.resource.org/cc/"
        xmlns:dc="http://purl.org/dc/elements/1.1/"
        xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
    <Work rdf:about="">
    <license rdf:resource="http://creativecommons.org/licenses/by/1.0" />
    </Work><p>

    <License rdf:about="http://creativecommons.org/licenses/by/1.0">
       <requires rdf:resource="http://web.resource.org/cc/Attribution" />
       <permits rdf:resource="http://web.resource.org/cc/DerivativeWorks" />
       <permits rdf:resource="http://web.resource.org/cc/Reproduction" />
       <permits rdf:resource="http://web.resource.org/cc/Distribution" />
       <requires rdf:resource="http://web.resource.org/cc/Notice" />
    </License><p>

    </rdf:RDF>


There is one that has whitespace (from line-wrapping) in some rdf:resource URIs, which I think is not permitted?

http://karlrichtermunich.blogspot.com/
        <rdf:RDF xmlns="http://web.resource.org/cc/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:rdf="
http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
        <Work rdf:about="">
                <license rdf:resource="http://creativecommons.org/licenses/by-nc-sa/2.0/de/" />
        </Work>
        <License rdf:about="http://creativecommons.org/licenses/by-nc-sa/2.0/de/"><permits rdf:resource="http://web.resource.org/cc/Reproduction"/><permits
rdf:resource="http://web.resource.org/cc/Distribution"/><requires rdf:resource="http://web.resource.org/cc/Notice"/><requires rdf:resource="
http://web.resource.org/cc/Attribution"/><prohibits rdf:resource="http://web.resource.org/cc/CommercialUse"/><permits rdf:resource="
http://web.resource.org/cc/DerivativeWorks"/><requires rdf:resource="http://web.resource.org/cc/ShareAlike"/></License></rdf:RDF>