I don't really get the idea of affixing permanent illustrations to your body. As an abstract concept, I see the attractions of wanting to make art that you think is cool part of how you present yourself to the world, and using tattoos as an emblem of identity. As a practical matter, though, I don't get it. Societal acceptance aside (and tattoos do seem to be more mainstream now), a design you love in your 20s may seem juvenile in your 30s, or embarassing in your 40s, or the execution of the design may not be what you expected. To say nothing of the fact that the canvas is sure to change, with unpredictable effects on the art.
However, I do know people with tattoos, who are enthusiastic about the decisions they've made, and since it doesn't affect me in the slightest, more power to them. Carl Zimmer (science reporter for the NY Times and blogger at Discover Magazine) has a collection of science-themed tattoos that includes some that I actually think are pretty cool.
I think we can all agree, though, that the horrible decisions made by the people displayed in the link above do an enormous favor to everyone they encounter, by graphically warning that their judgement should be trusted on absolutely nothing.