Facebook scans it to profile the sender's web activity.
They are correct, there's a bot that checks ALL links posted on facebook.
They use a spider called "facebookexternalhit" which they describe here: https://www.facebook.com/externalhit_uatext.php
Facebook allows its users to send links to interesting web content to other Facebook users. Part of how this works on the Facebook system involves the temporary display of certain images or details related to the web content, such as the title of the webpage or the embed tag of a video. Our system retrieves this information only after a user provides us with a link.
The real headline here should be: "US Law Allows Any Misguided Misinformed Moron To Sue Deep Pockets Looking For Handouts"