One WordPress blog can have many authors (called users). A user is more than a reader or casual visitor; they can add / edit / delete, thereby making the blog a collaborative effort. This is useful for an business blog.
To add other users, the owner of the blog must login to their dashboard and select, ‘Users, Users and Authors.’ They will be presented with the screen below. The example below has only one user who has administrator rights (the highest level).

Add users to your blog that can add, edit or delete posts and pages
New users can now be added. You can choose between contributors, administrators, editors and authors. Each have different powers. It is recommended that there be only one administrator.
Click here to learn about the differences between types of users
NOTE: All users for your blog must be registered with WordPress. They do not need to have their own blog however. They must personally visit WordPress.com, create their own user name, supply their email address and choose a password – then they may become a user for another blog but they can still create their own blog later on if they wish too.

Create an account on wordpress.com but do not ask for your own blog.
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