Blogs are an additional feature on PC and while everyone is free to comment on public blogs, they can only be created if you meet these criteria:
Become a Community Supporter of tier 2 or higher. (ie. donate at least $10)
Obtain at least 5000 posts.
Be selected by the staff.
Become a staff member.
As mentioned, there is a chance of being chosen specially by the staff for a blog. The staff may offer a blog to members who contribute actively to the community. If the staff believes you may have something worthwhile to contribute in a blog, there is a chance you will be selected to use the blogging feature.