if implemented, the linking would not be automatic. Basically the first time you used it you'd click the unmistakable "facebook connect" icon, and it'd bring you to a page on the forums asking you what to do.
If you weren't logged in, it'd ask you to either log in or register here. If you logged in and chose to link, it'd associate them. If you register at that point instead, I think it also sort of assumes you meant to register and auto-link (else you'd just click register without using the facebook connect thing, right?).
Beyond that, if it were enabled and you decided to link accounts and then decided to unlink later, there's an option in your profile to do so. Of course, that'd be contingent on facebook connect ... you know ... being implemented.
So far, we're about 50/50 neutral to negative, with nobody really chiming in as "on board". So I think it's probably off the table for now anyway.
