Some people have been forwarding me this email message that they received from Facebook:
The Simple Facebook Connect plugin has not used the FeatureLoader.js script since before version 1.0, which was released 5 months ago. Version 1.2 of SFC fully integrated OAuth 2.0 authentication, and it was released 5 weeks ago.
So if you’re getting this email from Facebook, upgrade SFC to the latest version. Problem solved.