Spam is pernicious because email is free. If there was a cost associated to email, then spam would become manageable. Of course, everyone gets antsy once you add money to the equation. So let’s consider some other ways of adding cost to email and see if we can’t find something that is good enough.
If we allow computers to respond, then challenge-response can be good enough. Suppose we were to build a Challenge-Response E-Mail Network (as opposed to Don Park’s Trusted E-Mail Network or TEN). Trusted nodes pass messages between themselves without challenge. But when an untrusted node passes a message to a trusted node, then a challenge is generated for every destination address. While not as effective as TEN, I think it avoids some of TEN’s bootstrapping issues.
Or how about artificially forcing email to be a one-to-one medium. We could require that each message had to be xor-ed with the destination email address for uniqueness, and hashed just to add some cost.
As technologists [and perfectionists], it’s hard to accept that good enough is good enough. But the economics of spam are based upon free email. If we can increase the spammer’s costs, then we can change underlying economic viability of spam.