There's definitely a trend with people I know using facebook's core functionality much less than we used to. While I still use it for event organizing, pictures, and occasionally chat, I barely write on anyone's wall anymore -- everyone I know uses their wall much less than when facebook was getting started. This is resulting in less social media use overall, rather than a shift to a different medium -- people I know use facebook/social media significantly less than we did 1-2 years ago. Funnily enough, this coincided with everyone's parents getting on facebook.