Turn an Old Computer into a Networked Backup, Streaming, or Torrenting Machine with Ubuntu. Know Your Network, Lesson 4: Access Your Home Computers from Anywhere. LH is often about how to get things done quickly, not how to do it securely.
Sometimes there's a difference, but I agree, in this case running VNC outside any sort of tunnel is a BAD IDEA. Allowing unencrypted VNC access from the internet is a noob mistake. Gee Mom, look what I did! Unencrypted traffic, often trivial password for access to the entire machine, anyone who can see the traffic can watch all your keystrokes. Turn an Old Computer Into a Do-Anything Home Server with FreeNAS 8.