Login w Facebook button being replaced with FB profile pic

That happens when you are in Facebook and have clicked the "Use Facebook As..." link and chosen a Facebook Page. The login with Facebook button (and some other social features) cannot be used when you are logged into Facebook as a 'Page'. Only real users can use some social features integrated into websites.

The 'Switch' link is Facebook's way of letting you switch back to your personal profile if you click it.

I hope that helps explain, but if not, just let us know.

Thanks,
Alex