Beware that a recent change on Facebook is putting your @facebook.com e-mail address as the displayed default instead of your original one.
There is reason for this in that if they keep traffic within the Facebook ecosystem and more people use the @facebook.com e-mail addresses then Facebook increase their marketing value even further.
For people like me with their own custom domain (alpagot.co.uk among lots of others), i'm sure they won't be happy that there was not a more 'in your face' warning. It's easy to go into your settings and 'reveal' your current normal email address again.
It seems the media outlets have picked this up as well and comparing it to what Google did with their Buzz service which failed horribly.