To be fair, the purpose of HN is to serve YC -- that's why we don't see ads on the site. People have suggested not scribd-ing everything before; I can only assume that the reason this has not yet happened is because the feedback we are providing is more valuable to YC than a few upset readers.

And this may well be the case: When most people have problems accessing a web page one way, they won't tell you directly; instead, they'll try to find another way to access it or give up. By providing only one way to read PDFs on a discussion board, you get access to this otherwise invisible negative feedback.