Regarding the wearing of stainless steel on skin, I think the answer is somewhere in between. Some of the links Lissa provides refer to toxicity when the metal is within the body / has access to an open part of the body, or else welding and fumes during the manufacture of stainless steel, things that would be expected to increase risk. Concentrations of metals within stainless steel also vary, as does individual susceptibility.
This document provides an interesting review:
http://www.ttl.fi/en/publications/Elect ... _steel.pdf
One of its conclusions is that "Based on the positive experiences of applying the release limits within EU, and on the basis of the studies referenced in this review, no sensitization classification is suggested for stainless steels with a nickel release <0.5 μg/cm 2 /week in artificial sweat (and <0.2 μg/cm 2 /week if used in piercing post assemblies)."
I'd be relatively confident about wearing stainless steel, but also recognize that risks (as with anything) cannot be completely eliminated, and individual factors may vary. If one has the option of reduced concentrations of nickel, all the better.