Steve,
I think Lars is right in suggestiing that the Internet Society
could issues certificates for its members. Such certificates would
imply only that the Society vouched for your identity in the context
of your membership, nothing more. It would be the electronic
equivalent of your Society memberhsip card, analogous to the cards we
get from ACM, IEEE, Sigma Xi, ... I would not characterize this as
a generic ID for someone, but it might serve a role in the same sense
that some of these other society memberhsip cards are used for rental
car discounts, etc.
Steve