it occurs to me that most of the methods that have been proposed
for filtering spam from mailing lists have a lot in common with NATs.
in both cases, the proponents say (in effect) "if it works for me and
for my small set of test cases, it must be okay to impose this on
everyone. if some legitimate traffic is excluded by my filters, they is
of no consequence - they should be willing to jump through whatever hoops
that I believe are appropriate. and if people have to abandon practices
that they find useful in order to to get around my filters, that is of
no consequence either, because they do not need to be doing those things
anyway"
Keith