We already knew that Facebook dominates time spent sitting at the desktop, but a new Comcast study using data from five top mobile operators shows that the social networker is by far the most used mobile destination as well. The study shows that  Facebook's 7.5 million unique UK mobile users spent 2.5 billion minutes on its site in December of 2010. By contrast, Google's 9.5 million users spent just 702 minutes on its sites.  The chart:

from Silicon Alley Insider