<http://schema.org/topics>
"craigslist,eHarmony,Facebook,flickr,friendster,google buzz,groupon,linkedin,Match.com,MySpace,Social Media,Social Network Lists,stumbleupon,Twitter,YouTube"^^<http://www.w3.org/2001/XMLSchema#string>
<http://mashable.com/2010/12/12/youtube-buzzed-social-network/>