Gold has value. It can be used by dentists. It can be used in electronics. It has been inherently valuable for millennia.
As I said, paper currency is too complex a topic to go into fully here. Unlike gold, it obviously is not inherently valuable. You can look at Weimar German marks, Confederate dollars etc. to see that. Or even a US 1978 dollar versus a US 2014 dollar, to some extent. People who think Bitcoins can be worth something because the dollar seems to have some value are going to learn a hard lesson.