Here is are article that tries to put some data behind Yoga and injuries, specifically what is claimed in the article you posted to and the book that it references. Not terribly surprising the injury rate from Yoga is significantly lower than that of weightlifting. Lifting is 4 times as high. It also points out that one of the studies that the book and article use was cited incorrectly to the point that the authors of the studies have refuted the claims made based on their study.
Interesting read, thanks for posting, i'm surprise its only 4x as high (based on how what i seen in the gym over the years), and not just from sloppy form, but also, from training muscles through positions of dis-advantaged leverage (which is why i now use static holds and limit my ROM on exercises). But as i stated previously, if the individual avoid's exaggerated ROM, lifts under control, smooth turnarounds etc, its a very safe way to train. The likes of John Little and Doug Mcguff have overseen 150,000 one on one HIT workouts with clients and never had someone get injured. In fact they've done their fair share of helping individuals rehabbing injuries. Personally, my injuries were caused from years of training my muscles through a "full range of motion", as well as high impact martial arts training.