Now, I'm hardly a vim expert, but isn't :w! force write? I believe :q! is exit without saving.

Indeed. Quite amazingly someone told the author in a comment only 2 years after the post was published in 2008 of this error.

Too bad the author didn't bother to correct this fatal flaw.

:w! is the command you execute to confirm that you don't have write privileges on the file you're editing.