It just cost too much money to produce for the viewing audience it received TN was cancelled basically because of economics, they set their goals way too high and it took too much CGI to accomplish it, and CGI is expensive.
Plus Stephen Lang surely doesn't come cheap after his success in Avatar.
Have you been keeping up with Falling Skies?
It's 3rd season starts in 2013 and if you liked TN you should like Falling Skies also.
The last I heard they said they were talking with other networks about picking them up. However I see the father in the show is now a main character on Vegas, so I am guessing another networking picking up TN didn't work out.