i think most people have a diary in hopes that someone will read it, or find it and think it is interesting and thought provoking; if it was to keep secrets or personal stuff why would you put it in writing. diaries are cries for help when you feel like you have no one to talk too. ....aaannnddd i took it to far.
I think it's good to share ideas and information with others as long as it's not too personal. The problem with sharing info online is that you can't change your mind once you publish it.
I used to have a diary when I was little. I think a blog is a great idea. I also agree with what Mr. Kazinec said. I have never had a blog but I think it would be a great thing for me. I could share my thoughts and they always say it is great to write down how you are feeling.