To be more specific, this is the HTTP response header that contains _some_ domains that resolve to the local loopback device, formatted to fit nicely.

    content-security-policy: 
         default-src * data: blob:;script-src *.facebook.com *.fbcdn.net   
         *.facebook.net *.google-analytics.com *.virtualearth.net *.google.com 127.0.0.1:*
         *.spotilocal.com:* 'unsafe-inline' 'unsafe-eval' 
         fbstatic-a.akamaihd.net 
         fbcdn-static-b-a.akamaihd.net 
         *.atlassolutions.com blob: 
         chrome-extension://lifbcibllhkdhoafpjfnlhfpfgnpldfl;style-src * 'unsafe-inline' 
         data:;connect-src *.facebook.com *.fbcdn.net *.facebook.net *.spotilocal.com:* 
         *.akamaihd.net wss://*.facebook.com:* https://fb.scanandcleanlocal.com:* 
         *.atlassolutions.com attachment.fbsbx.com ws://localhost:* blob: 127.0.0.1:*;

What's really fucked up, is that I am on my windows pc now, and I typed 'https://fb.scanandcleanlocal.com/' into my browser and it _worked_. It resolved to 127.0.0.1:443 and it just shows a blank page. My computer must have a virus.

Why would Facebook do that?

To talk to programs on the users computer of course.