<trollishly>
What do you guess for the amortized cost/spam?
</trollishly>
a cost that you are forced to pay in order to enrich somebody else is theft, no matter how microscopic the payment might be. "we all know what (they) are, now we're just arguing about the price."
I do find it amusing that nobody responded to my more relevant and intended thrust, about how putting a 'sender pays receiver for email' could cause a variety of new abuses of the email system.
on the one hand, you're right that any micropayment system would have to be very carefully thought out and even more carefully implemented, lest it open the door to many and varied forms of microabuse. on the other hand, that doesn't disprove the case, since even in your example it would merely cause people to become a LOT more careful about they mail they sent. that CAN'T be a bad thing. bill washburn's XNS effort, while nowhere near ready for critical review, shows some of the throught that needs to occur to make micropayments not be a bad deal for one or both parties. www.xns.org has an overview and www.onename.com goes so far as to say With an OneName solution, you control and manage all relevant identity data, with no need to involve a third party in your business relationships. You can customize authentication and permission structures for every business relationship and automate specific types of data exchange, both within and across the corporate firewall. These same permission structures provide an easy way for customers to provide consent for the usage of their personal data. note that i'm not advocating the approach, but rather, holding it up as one example of how personal messaging will have to work at "full scale."