Basic font-lock without font-locking double-quoted strings

[Joe Riel]

Why would the following minimal mode

(define-derived-mode msdbg-mode fundamental-mode
  (setq font-lock-keywords '(("EA" . font-lock-warning-face))))

cause text delimited by double-quotes, say

   "This gets font-locked"

to get font-locked?  Is this syntactic font-locking?
How can I turn it off in that mode?

If I set font-lock-keywords to nil, then the strings
don't get font-locked, nor anything else.

-- 
Joe Riel