Just with any form of physical movement, one can injure themselves if not being aware and sensitive to the signals their body is sending.
The article, while well researched, is entirely conceptual to this reporter. For example, despite Iyengar recommending the neck be flat in Shoulderstand, if the reporter had ever attended an actual Iyengar class, he would've written that an Iyengar teacher would NEVER let you have a flat neck in a Shoulderstand and insist you use 3 or even 5 blankets to prevent this.
The most dangerous type of yoga is fast paced, Vinyasa. This is where most people begin but because so little instruction is given and the dizzying pace in which people move in and out of Asana, most have very little idea what they're doing. I'm a full time teacher (of an Iyengar lineage) and receive people EVERY DAY whom have hurt their shoulders, low back, etc. in Vinyasa (including Vinyasa teachers).
This is a nice cautionary tale for people who try to force themselves into places their body is not ready to go... but a lot of it slips into silly sensationalism (the man who sat in Virasana for hours a day) and loses its original point of action.