The Price of Spam Would You Pay $1 a Year for Guaranteed Spam-free Email?

A few months back, my colleague, Matthew Hurst posted a link to a interesting infographic from the New Scientist that visualizes data from a spam-bot called "Storm.": (click the image the see the full-size graphic) The visualization is interesting, but doesn't explore what I think is the most interesting question with regards to spam: "what's the marginal revenue per spam email sent?" Based on some of the numbers presented, here's my math to back that number out: The sample contained 35 million spam e-mails, which was 1.5% of the total number of messages sent that month. Assuming the sample was random, a total of 2.33 billion spam emails were sent in a month, which extrapolates to 28 billion spam messages sent per year. The graphic also notes that "Storm" led to $ 3.5 M in sales for that year (via .000008% conversion). Dividing (sales of $3.5 M)/(28 billion e-mails), we get marginal revenue per email = $0.000125 dollars of revenue per spam message sent. $1.25 for every 10,000 messages. One of the main challenges with spam is that it's essentially free to send out. So no matter how effective anti-spam software continues to get, as long as a campaign leads to one single sale, the marginal profit is essentially infinite. Considering this from a regulation perspective, if the cost of sending out spam were to rise above $.000125 / message, spamming would cease to be a profitable business. So - what if  there was a required "e-mail postage", or (gasp!) an e-mail tax? Kinda like the USPS, but way, way, way cheaper.  And not because we need to pay for the cost of delivery (like Post Office workers) but as a means of cutting down, or even eliminating spam? I can feel the backlash from the Libertarian-leaning freemium crowd. What?! Tax?! The Internet needs to be free!? What about the unencumbered exchange of ideas amongst people!? Here's the back of the envelope calculation to consider the impact on a normal Internet user: If a normal-human-non-spam sends 100 personal messages/day, that would be 36,500 a year. At a cost of $.000125, that would cost a whopping $4.50. A year. Less than $.50/month. For guaranteed spam-free e-mail. Let's take the more realistic value of 25 personal email messages sent/day (about what I send), and it's about $1/year for an average user. (OK - yes, the mechanics of implementing such a system would be non-trivial.  But hopefully you buy that it's a) technologically possible and b) the marginal transaction cost would be $0.  If so, then we can leave the specification details for another day and I can keep the scope of  this post to economics and go watch the World Cup)