It's interesting that the only time Facebook seems to want to offer you any kind of emotional experience is when you're trying to leave the site, and the experience is designed to be a negative one, rooted in guilt.
Yeah. I'm not denying those kinds of experiences can happen on Facebook, but Facebook the company doesn't seem to care about making its users happier so much as it cares about keeping them on the site. Like network television or any other ad-supported medium, it doesn't need to be really good, it just needs to be minimally diverting. It's about generating addiction and not fulfillment.