sightfactory

The Restrict RSS Feeds plugin gives you several useful options for managing your feed such as:
<ol>
<li>Switching off all RSS feeds in your WordPress installation</li>
<li>Restricting access to authorized users by requiring a password for access</li>
<li>Removing descriptions and excerpts from the feed</li>
<li>Removing author names from the feed</li>
</ol>
RSS is a type of web feed that allows your readers to automatically get new content in email newsletters and RSS feed readers.
RSS feeds can be useful for your website when running a blog but are unnecessary if using WordPress as a basic website builder or ecommerce site. Some blog posts may also be gated content and be intended to be visible by authorized users only.

VisualWP Restrict RSS Feeds

A quick and easy solution to automatically disable all RSS feeds or restrict rss access with a custom password.

Clifton Griffin

Allows a blog administrator to disable all RSS feeds. (Useful for CMS installations or other situations where RSS is not helpful)
<h4>Version History</h4>
1.0 
* Original release.
Background:
Smashing Magazine suggested this hack. (http://www.smashingmagazine.com/2008/12/02/10-useful-rss-hacks-for-wordpress/)

VisualWP Restrict RSS Feeds vs Disable RSS