Random Thoughts - Portable Social Graph and URL shortners

Two completely disparate topics but my brain generally jumps from topic to topic almost randomly.

First, I listened to a great podcast this morning discussing how social media companies need to start thinking about ways to leverage the portable social graph.

Second, are short URL services harmful to search rankings? Google uses the context of the text of an anchor tag to help identify the landing link. URL shortners generally aren’t inserted into anchor tags. Also, since URLs are redirected, does it effect backlinking?