I would argue that the problem of ‘spam’ has not been solved, since that would mean an agreement on what constitutes spam—that spam has some inherent properties

I would argue that the problem of ‘spam’ has not been solved, since that would mean an agreement on what constitutes spam—that spam has some inherent properties that subjects it to easy classification, and that spam is not evolving. But that’s beyond the point that I originally wanted to make: spam and email have very similar parallels to security and the Internet. In another universe, it’s possible that the issue of spam and security could’ve been incorporated into the protocols themselves. But for some reason I’m sure is rational, those issues were moved outside, to the hosts — to be left to be solved with middleboxes as firewalls and Google’s spam filter. I would argue that this was the smarter choice and that both of these involve the same problem: spam and security are ill-defined and constantly evolving.