Originally Posted by Freeshadow
A fully embedded font could be used after extraction by the books purchaser. A partly embedded one will most likely have too many "holes" to be of use for pretty everything than the book it was shipped within.
Given that some of the fonts are costly I understand that a font creator rather dislikes the idea of people getting potential access to a font worth X after having paid just a fraction of ot for an epub file.
Although in practise, this is a silly fear. It might have been valid once, when computer fonts first came in back in 1987 and digital distribution was harder. In 2012, when if you want a font without paying for it there are numerous pirate sites and torrents, worrying about your fonts being embedded in documents is silly.
Just like publishers and DRM, really.