What are the dangers of giving out personal information online?

You should never put personal information into public areas of the internet. There are criminals who will take that information and steal your identity, then use your information to commit crimes and blame you for them! Personal information includes your real name, address, phone number, email address, age, sex, and anything else that a criminal could use to find out more information about you. This sort of information should only be given out to people you actually know in person, because you have no way of telling who you are talking to on the internet. The person who tells you they are a 14 year old girl (they may even show you a picture and say it is them) could really be a 50 year old man trying to commit a crime!
Because people can see your blog and comment on it
Blogs are like self-designed miniature websites that can be accessed by anyone. There are chances for the personal information of the blogger to be misused by miscreants. So it is always best to refrain from posting personal details on the blog.