This came to my attention via Eurobricks, and it has quite a lot of potential IMO. I love browsing through random stuff on brickshelf and LEGO groups on Flickr, and this might raise the visibility of great user content.
Courtesy of Eurobricks, here is the description of Rebrick from TLG:
What is the basic idea with ReBrick?
ReBrick is a social media platform where adult users can share and discuss user-created LEGO content online.
It will not be possible to upload content to the site. Instead the basic functionality is for the user to bookmark content from other sites, such as Flickr, Youtube, MOCpages and similar sites, and have a discussion at the ReBrick hub.
ReBrick is a public stage for fans of the LEGO brick to share their wonderful models and creations with the general public.
Here's the site, currently in Beta:http://rebrick.lego.com/