hmmm. This is a tough one. It all depends i suppose what motivations you have for doing it. There is a degree of risk to physical health in some cases, through blood loss or infections.
And the basic instincts of the pain response.
But it is your body .
Im not saying i frown upon it, its more that it saddens me.
i wouldnt be one to judge , ive been there done that many times.
But i was never happy doing it, it gave me no pleasure.