My two favorites aren't on the list, perhaps because they were never put in these exact words or they are mis-attributed:

"Cryptography is not magic pixie dust that you can sprinkle on a system to make it secure" -Bruce Schneier [? - couldn't find a good source]

"If you think cryptography will solve your problem, either you don't understand cryptography, or you don't understand your problem." -Roger Needham / Peter G. Neumann