Sometimes Simplicity is Only Skin Deep.
Some systems have a reputation for being simple, such as WordPress, but only as long as your needs are simple. The moment you need some high falutin' customization -- say, in this article, limiting access to blog posts to certain individuals -- things become way more complicated. I mean, you'd never have to go through this level of complexity in Drupal just to get to the same point. In fact, in Drupal, the capability is built in.
Controlling who is able to view a post is a simple task once the system is established. Limiting access to certain users has several applications, such as enabling a design studio to distribute artwork to its various clients, or enabling a small school to arrange for homework to be posted online using a cheap and easy solution.
UPDATE: Commenter Kyle Jones claims/alleges/would have us believe that there actually is a "plug-in" in Wordpress that achieves the same result. For the moment, we'll have to believe him :-)