Spontaneous end-to-end communication used to be the Internet's magic ingredient. But scarcity of IPv4 address space and legions of vandals resulted in NATs and firewalls. Now, unfiltered end-to-end communication happens, for the most part, by invitation only. Until recently, the lone exception was e-mail. You didn't need permission to contact someone by e-mail, and you could be reasonably certain that a message you sent would land in the recipient's inbox. Inevitably that had to change, too. The spam epidemic compels us to create and use the e-mail equivalent of NATs and firewalls: a combination of content filters, white lists, and blacklists.