The update does say its supposed to be "Invisible", but is actually instead just preventing people from registering at all.
They also seem to have a tendancy to move around quite a bit. I have managed to remove the custom fields part, but is there a way i can just remove this feature, because i can deal with spammers myself.. I'd rather people be able to signup than nobody at all..
The bug here though being of course.. why are these here at all?