I've stumbled across this issue a couple of times in the last while, where Chrome ignores autocomplete="false" and autocomplete="off". It will now even ignore autocomplete="whatever" or anything you do to trick it, if someone has submitted a form with that random "hack" in it before.
In trying to solve this issue, I came across this StackOverflow question, which doesn't solve the problem if you've submitted a form containing this field before.
EDIT: This is NOT for password fields.
