Permissions

I’ve seen on other blogs that the author sometimes turns over the permissions to post to his/her visitors. Sometimes the author has you login under a special name and password.
What I’d like to do this next week is set aside one day for visitors to be able to post. My plan is to allow visitors to register themselves at a level of “1” and set the ability to post to “1” as well.
Is this sufficient security to allow somebody to post a new message only? Not edit each other’s posts, not change the name of my weblog, not change security permissions, etc?