[css-fonts] defining font faces with an empty or white space only family name

I don't think the css-fonts specification says anything special about 
using a font family name of "" or " " when using @font-face.  Should 
either of these be disallowed?

http://mcc.id.au/temp/emptyfamily.html

Firefox, Chrome and Safari support " " while IE does not.  None of these 
browsers support "".