As the creator of this team blog, you have the ability to set the permission level of all participants. At the moment, only you have the power to edit all posts.
Each individual contributor is able to edit their own posts, and noone elses'.
Also, only you have the ability to change the gizmos and things associated with the design of the blog.
My suggestion is that you open such permissions to more than just you. But consider this carefully. If you offer everyone EVERY kind of permission, it DOES leave room for the old 'whoooooops-I-slipped' routine, where the entire blog is deleted by mistake while someone's editing something in the gizzards of the blog.