True, but not convinced enough people care about custom fonts over rendering an image. It ends up being pretty much the same experience for them. (Actually custom fonts may well load slower for users, so it's a worse experience in some ways).
eg:
http://docs.google.com/gview?url=http://infolab.stanford.edu...
Users won't see any difference, or care.
I do think scribd up to now has been pretty bad for the web, locking plain text documents and images up in their walled garden. Maybe they can change that, but what value can they actually add? What problem are they solving?