Thing 12 social media sites

I checked out Mixx, Digg, Newsvine and Reddit.  It takes a lot of time to figure each one out, but I can see the potential and why tech-savvy people would like to use it.  Whether it wastes time or enhances productivity would I suppose depend on the topic.  I used the share tools in a NYTimes article about Facebook, which was quite easy; someone else had already shared it to Digg.