When I was working with the late Gary Griffin years ago we did a great deal of research on the most common methods used at the time. We then sat down with an MD and tried to "plot" how the injuries would take place.
The number one cause based on what we found out was one that has not been brought up here and that is the use of recreational chemicals at the time one was performing their enlargement technique. Alcohol and many other substances change or alter sensations that would normally give a loud yell that it was time to stop. With the feedback network being short-circuited by chemicals serious injuries can take place.
A guy vacuum pumping in a hot tub with a few drinks in him is a very bad combination.
Individuals who promote some form of enhancement usually will describe all others as "dangerous". The problem is that they do the dish on all others first as if they are some incredible authority before they get to the punchline regarding their own promotion in place of it.
All of the dangers which are serious result from one single event. That one single event is the interruption of blood flow and thus oxygenation to tissues involved. With few exceptions and unless we are talking serious impact, the penis is as a whole a pretty resiliant organ.
At no time when you are doing anything regarding PE should you be using any form of pain killer or even common analgesic. Aspirin is a blood thinner and in and of itself can cause problems if a capillary breaks.
Every human being who undertakes a PE program is going to have times in the progression of their efforts that they push the envelope too far. Usually this may be a blister or two, it may be soreness of the ligament structures that lasts a few days, it may be some minor bruising.
If you look at percentages of the men who have tried PE via mechanical or manipulation techniques versus the number of major disasters that have taken place when that same portion of the anatomy is attacked by a surgeon, the odds of injuring yourself are far lower than the odds of a surgeon doing it.
Oh, by the way, the greatest number of those screaming about PE are in fact PE surgeons. It is wrong if you do it, but if you do it post-operatively, we call it stretching and then it is OK.
Any PE program takes time perserverence and dedication. If you make the decision to undertake a program be aware that as a usual rule, actual measurable gains do not take place overnight. You are going to be doing this for a period of years to get decent permanent gains IF you are a person able to gain via these techniques.
Ligament structures and their nature varies from individual to individual and there is no way to predict the small percentage who will find that they lave ligaments the equivalent of high tensile steel.
The rule is good common sense. . .