I'm one of those middle-aged users of Facebook. What I find appalling about Facebook is how much its context changes users' online behavior. Many of the people on my friends list of Facebook are people I also know from specialized, topical email lists. On the email lists, the people are serious and thoughtful, but on Facebook some of the same people let loose with a bajillion "What grocery produce section vegetable are you?" quizzes and endless flair and bling and mafia wars. My friends are less my friends, and more of an annoyance, on the Facebook platform. Facebook turns adults into kids.<p>So although I appreciate Facebook for linking me up to a few former classmates from childhood (my first Facebook friend was one such), if I want to do what I really enjoy, as a grown-up adult, I look for those same friends in other contexts. And that, I think, is why Facebook is extremely unlikely to build a business model through which it can gain more revenue per user than it has expenses per user to serve up cute photographs and videos.