That's one of the features recently added.

A Trackback is a refernce to see when somebody links back to a web page.
Trackback defenition

Lots more cool stuff we'll get to add very soon:
New Customizable Member Profile Page
User-Created Social Groups
User Picture Galleries
Public Messaging
Reciprocal Friendships Between Users
Thread Prefixes
Thread Tagging
Social Bookmarking of Threads
Attachment Viewing Lightbox
Visitor tracking on profile pages

And good news for us (webteam):
Inline Spam Management and Prevention Tools
New Human Verification Systems