Fred has a killer post up on the economics and finance of Facebooks apps, riffing off of Valleywag’s hype-busting post. But Fred’s post really moves the ball forward. My experience on Facebook apps? Near the top of the messages I see when I visit Facebook are the numbers of my friends who’ve uninstalled apps. I bet the churn is off the charts – I’ve no doubt that social media sites like Facebook are here to stay, but we are awfully early days just yet, and people are playing with their toys. Update: Marc Andreessen appears to agree on the last point.