By Turning off user registration for WordPress Blogs, you can save a lot of time by not having to remove spam accounts or cleaning up their spam comments. Plus, it might increase your sites security since visitors can’t use your back end of your WordPress blog. They can just comment. If you have a high traffic blog, there can be hundreds or thousands of spam bot registrations a day which can really clog up your database table for WP_Users and make you run out of space for posts, plug-ins, etc if your database size is limited to 100MBs or less.
In my experience, most of the members who tend to register for memberships tend to be spam bots, or spammers, and commenters usually don’t join a blog to comment. They just comment by filling in their name, link, and e-mail from the comment form on each posts and page in WordPress Blogs.
Unless you run a giant blog with lots of traffic like Gawker, Engadget, etc with a lot of spam from guests, you probably do not need Member registrations to comment.
1. Click Settings then General in WordPress Dashboard.
2. Uncheck the anyone can register check box in General Settings’ Membership setting.
3. Click Save Changes at the bottom of the page.
Now no one can register for your blog, so you should have fewer spam bots, and spammers who use up all your database space by registering on your blog and posting spam comments.