thoughtbot/bourbon — pull request #96 by javasteve99 (2012-05-01 12:55:37+00:00)
Title: Update hide-text mixin to use a simpler technique with better performance.

Based on the following article I'm recommending a change to the Phark image replacement technique:
http://www.css-101.org/articles/image-replacement/the_new_new_image-replacement_techniques.php

Most people are familiar with using text-indent: -9999px; but this practice has been called into question because it draws a 9999px wide box that extends off screen, which can adversely affect performance. By going back to the original method which includes overflow: hidden; we can avoid the performance hit by preventing the box from being drawn at a size larger than the visible area of the element in question.

The article does a great job of summarizing the pros and cons of the various methods available.