Personally, I use JungleDisk (which was recently acquired by Rackspace) to encrypt all my data and back it up to Amazon (on my own S3 account, not JungleDisk's). Sure, it costs more than Dropbox or Carbonite or other services but it seems incredibly more safer and controllable to me.
On the other hand, I use Dropbox to synchronize non-sensitive files between my machines. I never put anything on there that I'd be worried about being published unprotected to the world.
On the other hand, I use Dropbox to synchronize non-sensitive files between my machines. I never put anything on there that I'd be worried about being published unprotected to the world.