I'm not sure why that is. Personally, I think whatever style the business itself uses is the right way to go, but I was once corrected by a client for using the lowercase 'f' when referring to the social media site.
I have noticed sometimes Goodscribble is written down (by others) as two words, 'Good Scribble'. Yet my business name has always been one word in my mind, and in my branding.
There's no way to control what people do with your business branding once it's out there, particularly in this age of social media engagement. And I don't suppose the people at facebook especially mind which case is used, so long as people are talking about it.
But consistency is worth striving for in everything you can control.