As I reported on Facebook and in my blog.
When switching over from one account to another, email is not switched over. So if someone asks you to use your phone to check facebook, they could be reading your facebook email.. Read more
http://sandsquidsblog.blogspot.com/2010/04/facebook-security-bug.html
Hi,
Thanks for the tip and making us aware. Keep us updated on what you hear.
Doc
Did you trying contacting Facebook about this bug? Thanks for the tip.