I bet that @font-face will be the most stupid mistake they make into CSS.

It will allows HTML content to be disconnected with which actual user read.
I can write “Cat” in a HTML but apply a custom made font to display “Dog” to the user. I think the SEO and page-rank cheater will like that. It is relatively hard to detect by robots compare to img/display/javascript content patching.

I believe most search engine service provided do not want to see it happen.

Ref: font-face
http://www.qodo.co.uk/blog/re-introducing-font-face-css-rules/

CSS Hide