FaceBook. Got talked into it last week, and suddenly "friends" are crawling out of the virtual woodwork.
Of course, the same is true of blogging in general. Any time a person puts anything up on the web, unless they embed something in the photo, like a nice diagonal overlay screaming COPYRIGHT in humongous letters, it's at risk of someone else doing a cut and paste and re-using it. About all one can do is hope that anyone lifting something is nice enough to tell the rest of the world where they found it. No, realistically the danger with FaceBook isn't anyone stealing my deathless prose -- it's me wasting more time than I should on an activity that's as ephemeral as an Atlanta snowfall.