Interesting: When you copy text from a New Yorker article and paste it somewhere else, it automatically includes a “Read more: URL” at end of paste.
Then pasted it into an email and it showed up like this (with “Read more” link):
NY Post (and others?) also doing this.
Update: Tynt is what these sites are using. “Measuring reader engagement by how often they copy and paste” talks more about how sites use the data generated by Tynt. [thx ZS]