I'd ignore this feedback for now. I'm not saying that these people aren't important, just that you sound like you're solo like me. Stay focused on your product. These folks will eventually come in from the wild once the product is good enough and they realize that you're using fbconnect like they use the power company.
Email followed distantly by twitter and openid. The only reason twitter is there is that I have an account, but don't use it or care about it.
More importantly I will never use facebook to signup somewhere else. I don't want random services anywhere near my facebook profile.
I still use old school email for signups when I can.