If you have 2 websites, one with Facebook Connect button prominent on the homepage, the other one displays Facebook only if you click or mouseover on signup link/button.
Do you think people will more likely signup on the first website just because of the Facebook button?
like: "great there is a Facebook Connect! I signup."
Or at the opposite, the value proposition of your website should be strong enough to encourage users to signup and then provide the conveniency of Facebook Connect at that time.
PS: Some of you will probably tell me that it is better to have the Facebook button right away, but the underlying theme of this question is having a good balance between minimal design and conveniency.