All Complex Ecosystems Have Parasites

and diversity lets all kinds of innovative stuff happen: if you go to nytimes.com and "send a story to a friend," the NYT can convincingly spoof your return address on the email it sends to your friend, so that it appears that the email originated on your computer. Also: a spammer can harvest your email and use it as a fake return address on the spam he sends to your friend. Sysadmins have server processes that send them mail to secret pager-addresses when something goes wrong, and GPLed mailing-list software gets used by spammers and people running high-volume mailing lists alike.

You could stop spam by simplifying email: centralize functions like identity verification, limit the number of authorized mail agents and refuse service to unauthorized agents, even set up tollbooths where small sums of mo