A blog or a diary?

For those who remember, before there were blogs there were handwritten diaries.  I suppose they are essentially the same in many ways.  However, there is a distinct difference in that diaries were intended to be private or at least for a very limited audience whereas a blog is quite the opposite.  I still find it funny how some people want to share everything about their lives.  I have never been that type which is why I think I prefer the idea of a diary.  It's more of a documented set of notes to yourself for your own use or reflection.  There's nothing wrong with either but I suspect that you may find that people prefer one over the other.  That could make for an interesting survey or psychological investigation depending upon how far you may take it.