Sending huge numbers of e-mail messages costs spammers very little, since the costs of e-mail messages are spread out over the internet service providers that distribute them (and the recipients who must spend attention dealing with them). Thus sending out as much spam as possible is a rational strategy: even if only 0.001% of recipients (1 in 100,000) is converted into a sale, a spam campaign can be profitable (Mangalindan 2002). Spammers are demanding valuable attention from potential customers, but they are avoiding paying a fair price for this attention due to the current architecture of e-mail systems.
One way this might be implemented is by charging senders a small fee per e-mail sent, often referred to as a “Sender Bond.” It might be close to free for an advertiser to send a single e-mail message to a single recipient, but sending that same e-mail to 1000 recipients would cost him 1000 times as much. A 2002 experiment with this kind of usage-based e-mail pricing found that it caused senders to spend more effort targeting their messages to recipients who would find them relevant, thus shifting the cost of deciding whether a given e-mail message is relevant from the recipient to the sender Closely related is the idea of selling “interrupt rights,” or small fees for the right to demand one’s attention (Fahlman 2002). The cost of these rights could vary according to the interruptee: interrupt rights for the CEO of a Fortune 500 company would presumably be extraordinarily expensive, while those of a high school student might be lower. Costs could also vary for an individual depending on context, perhaps rising during the busy holiday season and falling during the dog days of summer. Interruptees could decline to collect their fees from friends, family, and other welcome interrupters.
Another idea in this vein is the creation of “attention bonds,” small warranties that some information will not be a waste of the recipient’s time, placed into escrow at the time of sending (Loder, Van Alstyne & Wash 2004). Like the granters of interrupt rights, receivers could cash in their bonds to signal to the sender that a given communication was a waste of their time or elect not to cash them in to signal that more communication would be welcome.