Concentration camps in our own country?

Last week in class we talked about concentration camps and labor camps like the Gulag's that Stalin made and Nazi concentration camps Hitler made. We also learned that there are still concentration camps to this day like the ones in Siberia,  Darfur, political concentration camps in North Korea and religious camps in China. The question was raised of how these countries could still possibly have camps to this present day, and how the general public is not aware of these things. The scarier thing is that this could possibly be going on in our own country too, watch this...  http://www.youtube.com/watch?v=0P-hvPJPTi4&list=QL&playnext=1