[jzelinskie]

This trope definitely didn't begin in 2009, as "the hikikomori anime", NHKにようこそ, was written in 2002 and adapted to anime in 2006. Maybe it's been more popular recently, but most anime are adaptations of some other format that have already been successful over the course of years. Something to keep in mind is that anime/manga satisfies a niche market and the hikikomori are actually a demographic for sales; making content that appeals to your demographics is good for business.