In the past, whenever I signed up to some web app with Facebook, I got the option to give them a custom email address instead of revealing my Facebook email address.
It now seems to be gone:
There used to be a dropdown allowing me to select a "secret" address. Is there really no longer a way to sign up with Facebook without giving them my Facebook address?
I use a custom address for every website so that I know who leaked it to spammers and have a trivial way to permanently block it; that's why I'd rather not reveal my Facebook email address.