It is hard to capture the "flow" of a business process with words, just like it is difficult to grasp the aural universe(s) present in the score of a late Beethoven quartet.
Jim McGee of JVM Associates* provides a striking visual explanation of the reason for the superiority of wikis as a collaboration tool. Just like the "Yays" and "Boos" of the Common Craft video, this diagram (once you get past the smiley faces) says it all. Users have to do roughly more work more often with email. It's time to wikify the law firm!
*Thanks to Dennis Kennedy for the tip, from his weekly links.