Video - Women at CrossFit Santa Cruz doing kipping pullups. Kipping pullups come in many different forms. Over time each person develops their own style. If you look at this video directly on YouTube here:
You can see many comments from people who do not understand the benefit of this style of pullups. The purpose of the kip (swing) is to perform more work in a shorter amount of time (greater average power output). This provides a potent stimulus that helps improve fitness.