There's some guidance on the Microsoft website targetted at helping both parents and children to blog safely - click here to view it. I'm sure we've all been amazed at how much personal information the average teenager gives out on their blog. The naive idea that posting to their blog is just like talking directly to friends. In my experience human nature leads us all to be trusting by default and cautious as an after thought - particularly online. If you have something interesting to share with close friends then bear in mind that by default ANYONE ELSE ON THE INTERNET could view your post. Perhaps you should set up restricted access to your blog and limit it just for your close friends. Perhaps you should change some of the details (names, locations etc) - your close friends will still know what you mean.
Check out the guidance for more ideas.