It's a fair point about PDF but a balance should be struck somewhere, nowadays vast majority of users are not power users and if they have to have a separate piece of software installed as a PDF viewer that means it has to be kept up to date as well as the browser, and if they don't they'll be more succeptible to being offered malicious or dangerous viewers (*cough* like the adobe one *cough*), while a browser one could be sandboxed and would "just work" (hopefully (who am I kidding)) and would have more frequent updates.
Biting the hand that feeds IT
