Tattoos: Self expression or Self mutilation?

For so many years society as a whole would deem any form of poking or cutting yourself with needles or knives as a form of self mutilation. But at some point a transition was slowly made, where now people are encouraged to stretch, pull, pinch, cut, insert or mark up their entire body. In fact there is probably less then a degree of separation between those with body adornments and those with none as proof to how accepted this has become.

 If our body is a "temple", and we are putting constant permanent graffiti on the "walls" as well as opening new or enlarging old holes, then that would definitively be the most unholy of practices.

Is it just self expression or is it in fact a form of self mutilation that has been approved by society?