I probably do overshare, but I also lock my journal, so I can control who sees what. I would likely post in a different way if I was blogging publicly or on a different site, but the "journal" nature of LJ and the flock feature allow, and possibly even encourage sharing more. The other thing about LJ for me is that pretty much all of my friends are on it, but because of the distances between us we can't physically talk often. So my journal is how I connect with them. I actually usually feel more discomfort about oversharing when I write fic than when I post in my journal, though - I think fic often reveals much more about me than my everyday chatter!