I didn’t realize that WordPress has a Private setting for blogs until I ran across this notice when I clicked on a blogger‘s profile –
This site is marked private by its owner. If you would like to view it, you’ll need permission from the site owner. Request an invite (link removed by me) and we’ll send your username to the site owner for their approval.
I decided to check out the setting. I found it under Manage -> Settings; I wasn’t sure if it would be under Manage or WP Admin.
Your site is visible to everyone, and it may be indexed by search engines.
Your site is visible to everyone, but we ask search engines to not index your site.
Your site is only visible to you and users you approve.
My blog is set to Public. I don’t mind search engines looking for it.
For the blogger who set it to Private, I am sure there is a reason, but from what I saw posted publicly, it does not appear related to what they blog about. I can see the advantages of setting a blog to Private in certain situations.