Tyler Cowen points me to this case against YouTube. In short, the user generated crap which dominates the system costs money to host and serve, but doesn't offer much of a return in monetization. But it seems to me that this is just the problem of too much crap on a lot of these "social network" driven websites where sorting for quality hasn't been well thought out. After all, I still have a woman on my gtalk list who I purchased a bed from via craigslist 3 years ago (we both had gmail addresses we used for email). I should probably prune her from my list, along with the other random people who I've emailed with but don't really know.