Is it really any use trying to enumerate all variants under *.facebook.com and similar?
The counts:
307 facebook.com
295 fbcdn.net
250 tfbnw.net
12 whatsapp.com
9 instagram.com
3 fb.com
3 edgesuite.net
2 metrix.net
2 fbsbx.com
2 fbcdn.com
2 facebook.net
2 edgekey.net
2 cdninstagram.com
2 akamaihd.net
1 fb.me
1 appspot.com