My undergrad thesis, written four years ago, was a taxonomy of anti-spam systems. Since then, every anti-spam system that I've seen both (1) falls neatly within one of my categories and (2) fails to account for the problems I identified in that category.

This idea is an authentication-based system, because it relies on identifying the message sender in order to prevent spam. Among other things, it fails to account for identity theft.

For reference, here is my thesis: http://www.eecs.harvard.edu/~cduan/download/?file=thesis.pdf

It is an interesting thesis, but some of your points, such as the one that people with spam filters gets as much spam as those without, seem a little dated. Since I switched to GMail I have gotten practically no spam.

I think it is worth noting this form: http://craphound.com/spamsolutions.txt

And in short:

(X) users of email will not put up with it

(X) requires immediate total cooperation from everybody at once

(X) many email users cannot afford to lose business or alienate potential employers

specifically, your plan fails to account for:

(X) extreme profitability of spam

(X) joe jobs and/or identity theft

(X) extreme stupidity on the part of people who do business with spammers

(X) dishonesty on the part of spammers themselves

(X) outlook

and the following philosophical objections may also apply:

(X) whitelists suck

I would like to conclude that this is not some snarky elitist comment to this insightful blog post. I'm simply stating that spam is a very old problem, and many people have spent a lot of time trying to stop it. This form exists as a reminder that many of these options have been thought up before, tried, and found to fail. We've learned from some of our mistakes :)

Just because spam is an "old" problem doesn't mean it's not solvable. For example, if someone were to build a working prototype or something that demonstrates to advertisers that a pull method actually works better for generating sales/ interest/ revenue than spam, companies might be more willing to invest in infrastructure conducive to pull.

Spam is "profitable" because of the low cost of spamming a bunch of random people at once. I think the article is making the point that there are alternative low-cost solutions which can be targeted more precisely to an audience that is actually interested in the source of the "spam," thus making it much less annoying.

That for exist so people on slashdot can write a post before they loose interest. Half of your points assume _everybody_ is going to use this system and the other points are simply wrong.

We already have this: Twitter DM

This is promising. Probably the best technical solution to spam I've heard. Twitter + PGP + Good UI could work ....

You don't want the security PGP provides. You probably want a different one: http://en.wikipedia.org/wiki/Off-the-Record_Messaging

"The primary motivation behind the protocol was providing deniability for the conversation participants while keeping conversations confidential, like a private conversation in real life, or off the record in journalism sourcing. This is in contrast with the majority of cryptography tools which resemble more a signed writing on paper, which can be later used as a record to demonstrate the communication event, the participants, and the topic of communication. In most cases people using ordinary cryptography software are not aware of this and might be better served by OTR tools instead. The initial introductory paper was named "Off-the-Record Communication, or, Why Not To Use PGP"."

If nothing else this is an interesting view of the problem. However, changing the vast sea of legacy systems based on the crusty SMTP protocol is a nightmarishly large task. Lately I've been enjoying things like Twitter which are not bound to the old push methods of yore. :)