How is politico.com inserting a hyperlink into copied text?
<p>If you visit <a href="http://www.politico.com/news/stories/0509/22574.html" rel="nofollow">this article</a> on politico.com, highlight some of the article text, then paste that text elsewhere, it will contain a link that says "Read more at: ...".  How is this done?</p>

<p>Update: This is the JS used, but hard to follow: <a href="http://tcr.tynt.com/javascripts/Tracer.js" rel="nofollow">http://tcr.tynt.com/javascripts/Tracer.js</a></p>
