From previous experience on integrating Facebook Connect into a site at least 1 extra database field is required for more reliable logins (a standard "email" and a "facebook" email, not everyone uses the same emails across both systems, or a field to store the users facebook id).
It also requires some kind of JSON class to be used (unless you hack together some code using Instr and Mid's), some Base64Decode functions and b64url_hmac_sha256 (google that and Javascript).
After all that extra code, it can be done :)
Bruce, If you are seriously thinking about adding this (please do!) and need help, send me a PM

I spent a few days pulling my hair out until i figured out all the crap it takes.