By 'paradise' they of course mean warzone. We can randomly generate worlds and then add unique environmental elements like caves and waterfalls. Don't forget those miscellaneous objects!
We can create, share and download new stuff to keep the game fresh. Make something good enough and it could appear next to official Ubisoft released content.
Far Cry 3 releases on Xbox 360, PS3 and PC November 29th in EU, 30th in UK, December 4th in the US.