Who wants to work in a fast-paced environment? Not me! I want a civilized environment where people have a sense of balance. Higher quality work gets done that way and work life isn't full of stress and anguish. 
It's code for "We change our minds a lot about what we want from the software, and if we hire you we don't want you to complain about it.  In fact, we expect you to put in a lot of overtime to implement our latest whim decision because we're fast paced. You've been warned."

In programmer-speak, it means "we have no specs, unit tests, or for that matter, anyone still around who remembers why our software is the way it is."
