Umm.. Before deciding what sites should or shouldn't be doing, did you
actually check WHY they are setting cookies?
www.ripe.net sets 2 cookies for me :
serverid=ws-www-plone2
wdm_last_run=1358067104394
The first of these is a fairly typical cookie for sites to set, and is
normally use for session persistence when load balancing.
The second seems to be related to something they are running to check IPv4
and IPv6 connectivity, and specifically controlling that it only gets run
once for each client. That seems to be a perfectly acceptable use of
cookies for me, and is something that could not reliably be done any other
way.
Scott