I think a lot of people (me included) just though of Scribd as a YouTube of documents -- taking advantage of unlicensed material to juice up Pagerank, and then somehow converting that into a revenue stream. It also seemed kind of annoying to launch a Flash player just to view a PDF in a now, double-scrolling window, however I'm reminded, while reading this technical post, about the Ycombinator interviewer who said: "where's the rocket science?" Clearly, we're seeing some smart developers tackle a tough problem, and for a broad audience. I think they have a bright future!