While there are certainly people (especially on HN) who are unwilling to give Facebook this kind of control, I don't think it will be a problem for the vast majority of users. In my opinion, the power of having an identity behind all of your users far outweighs the cost of the few who will not use Facebook Connect.
I'm not sure this is a reliable way to get an identity behind all of your users. It was reliable back when Facebook required .edu email addresses, but these days there are huge numbers of fake profiles, and it's easy to create a throwaway profile if you need one to sign up for a site.
