They just turned those former pirates into a revenue stream. It's a good business move. Either spend tons of money litigating pirates to just have them go somewhere else, or at least make some money off of the inevitable.
Yeah, but these pirates put their own DRM on everything and generally get in your way as much as any publisher paywall. This is more like hiring Hell's Angels to provide event security.
It seems that scribd's business model now more prominently features selling access to publisher content - seems like a fine decision to me.