As a site owner you should probably have both. FB connect isn't "free": implementing integration probably takes more time than installing authentication plugin for Rails (and doesn't Django have built-in user management?)
But I think you should have Facebookless login if you care about early adopters: too many of them are indeed "outliers" you've identified above. I also think you should have facebookless option simply because it's good for the Internet: I wouldn't want to see so much of it being controlled by a handful of large corps.
Looking at the crisis of social security and "performance" of my modest 401k funds I sometimes feel that my own successful startup (with a modest exit) may be my only way to escape extreme poverty at older age. I doubt that anyone will hire a 65 year old programmer and I just don't see how SS+401k will be enough to deal with living/medical expenses. In that sense I'm desperate: starting a successful project is matter of survival.
But I think you should have Facebookless login if you care about early adopters: too many of them are indeed "outliers" you've identified above. I also think you should have facebookless option simply because it's good for the Internet: I wouldn't want to see so much of it being controlled by a handful of large corps.