I have made the sign-up to MyBloggers private. The main reason was spammers from China, India, etc. You may or may not have noticed the absents of a sign-up button or link...that is because I have removed them. Tricky, aren't I? :)
If you know of someone that would like to become part of the MyBloggers family, you can still use the Invite Friends link. This will allow them to register for an account, and it will automatically make them one of your friends.
Think of MyBloggers now as a private club!