Carl,
I see your point about various forms of purported affiliation,
but I think X.509 certificates are analogous to only one of the
examples you cite, namely the student ID card. The sole purpose of a
certificate is to establish a binding between a DN and a public key,
vouched for by a CA, and that seems highly analogous to an ID card
which establishes a binding between a name and a picture, vouched for
by the card issuer (the University). I can't really see that a
certificate is analogous to a sweatshirt or a bumper sticker
emblazoned with a university name and logo. (It might be worth noting
that when someone markets sweatshirts, they do so with explicit
permission of the university if a reasonable likeness of the
university logo is employed. Maybe this is getting too far into
analogy details ...)
Steve