An increasing trend is opting to disclose content only to registered members, sometimes on a premium basis. WordPress has a great user system, with the potential to grow through a range of available plugins so this shortcode can be requisite of your circumstances. By simply using this shortcode, any content that falls between the tags will only be available to those currently logged in.
If your worried about your feed, this shortcode will also put hide the content there, so no loophole is to be found.
As you may (or rather, should) be able to tell from the shortcode function above, the [member] tag will render any content that resides between it invisible to users that are not logged in, or viewing the feed.