I don't think he's implying social networking will go out of fashion, but that social networking companies themselves can be fashionable. For instance the progr

I don't think he's implying social networking will go out of fashion, but that social networking companies themselves can be fashionable. For instance the progression of "cool" social networking sites seems to progress pretty rapidly e.g. myspace -> facebook -> twitter -> instagram -> snapchat. To put it in Steve Blank terminology he likes to invest in companies that face invention rather than market risk.