Anyway, unless you do want one, check your account. My settings are never changed by these "Hurry! Facebook changed all your settings and now [insert frantic warning about invasion of privacy]!" messages, but it was this time. So check it out if you care.
http://lifehacker.com/5921095/facebook-just-changed-your-email-without-permission-heres-how-to-get-it-back?utm_campaign=socialflow_lifehacker_facebook&utm_source=lifehacker_facebook&utm_medium=socialflow