I have talked about privacy before, but many of us like to put a lot of ourselves online, through blogs, Flickr, Twitter, etc.
What do you leave off? I leave out lots of family details, even if they are public record.
Also, there are many messages, particularly on Twitter, that I do not send, even when I am bursting to vent. Much of my online life is professional, and there are professional, competitive and ethical considerations.