You should check out PostSecret. I still haven't figured out what makes me love it so much... I just do.
Maybe it's the sense that someone is telling me their secrets... that someone trusts me. It feels nice, especially when I have friends that don't even trust me. Maybe it's the fact that right there on that screen, there's something, be it work of art or almost post-it quality, that I can relate to. It makes me feel a little more human. Maybe it's simply the fact that I really like hearing juicy gossip, even if I don't know who it's about.
My guess would be a combination of the three.