What this represents, it seems to me, is the transformation of our common cultural understanding of human corporeality, from contingent assumption to axiomatic locus of meaning - in other words, from something we take for granted to something we feel compelled to obey. This is what unites a broad array of practices and symbolic representations, from personal behaviour to public broadcasting and all that unite the two.
From being the most immediate of categories, the body has become one of the most mediated, attuned to priorities beyond the self in the hope that this will put some flesh on the bones of the self. Tattooing and piercing are thus brought into the mainstream of fashion, tweaking the flesh in the desperate attempt to connect inner need with outer norms, through the medium of a corporeal statement. Transcendentalism is literally written on the flesh - in Sanskrit in the small of the back, maybe, a perfect expression of the solipsistic silliness of such acts.
The first paragraph above is an interesting take on contemporary narcissism, although the idea about the body as a contingent assumption puts me in mind of a conversation about Sebastian's decline between Charles Ryder and Brideshead (Sebastian's older brother) towards the end of Waugh's novel in which Brideshead shocks Ryder by considering his brother's phyiscal woes as insignificant compared to his moral condition.
Can't say too much about the second paragraph because I know someone who I certainly think would benefit from thinking about it.
If that all seems a bit po-faced, here's something a little more light hearted on body art. The highlight being:
When he copped for an arrow on top of Senlac Hill in 1066, King Harold's body was identified among the pile-up of his followers because he had the words "Edith" and "England" tattooed on his chest.